TAC Tech => Mechanical => Topic started by: Zach on February 10, 2023, 10:05:24 PM
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Howdy,
Recently took apart the Quadrajet and rebuilt it using cliffs book, SR kit rebuild kit, and a bunch of youtube videos but I am having some issues. I was able to get the car running and idling fine, still need to test and tune the high idle and choke because I think it isn't working properly, but besides that it idles steady and works as it should at operating temp. However, I have a lingering issue that also happens to be the main reason I rebuilt it in the first place. There is a consistent spot on part throttle that has the tendency to bog the Quadrajet and at the most extreme if I hold it right eventually kill the car. Some more specifics on the issue is that it happens on a consistent part on the throttle position, pedal is depressed roughly 2 inches, Only happens when I rapidly press the pedal, really noticeable on moderate revs at idle, you can ease by the "death zone" but it isn't easy due to how early it is on the throttle, not as noticeable when the car is up to speed, most noticeable from a dead step or simply idling. After extensive research my two theories are a faulty accelerator pump mechanism, and running to lean. During my rebuild I fully replaced the accelerator pump and made sure the walls were squeaky clean and I couldn't see any glaring issues. I left pretty much everything stock inside the carb and either cleaned, replace with a new part, or used the old part, no upgrades or anything like idle tubes, jets, etc. I was just hoping on getting some input on this issue if it sounds familiar, or can tell me how to diagnose it better. I am also fighting around 20ish degree weather in Minnesota so it isn't ideal for tuning and running, as well as the inability to test drive but I don't think these issues should still be relevant. Currently waiting for verification on cliffs forums, but would like to hear from you guys as well.
Any questions or you need more info let me know, I probably left out some information that I cannot think of at the moment,
Thanks.
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I’m kinda having trouble understanding the circumstances that exist to create your problem. You mention it occurs when you hood the throttle but then mention rapidly pressing the pedal. Does it occur under a load only or will it do it in park/neutral too? Just need a little more info to clarify but to be honest if you posted over at cliffs, I have no doubt you’ll reach a resolution there.
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I’m kinda having trouble understanding the circumstances that exist to create your problem. You mention it occurs when you hood the throttle but then mention rapidly pressing the pedal. Does it occur under a load only or will it do it in park/neutral too? Just need a little more info to clarify but to be honest if you posted over at cliffs, I have no doubt you’ll reach a resolution there.
Sorry, sort of just typed all the info out quick since it was fresh in my head. Basically if you press the pedal down, my estimation is around the 2 inch mark(about the same throttle range as if you were revving it), it will bog and if you were to hold it in this spot it could eventually kill the car. It occurs any time you give it that certain amount of throttle, but it is most noticeable when parked. Essentially it is a very large hesitation that can cause the car to die out if held in that specific zone.
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I’m kinda having trouble understanding the circumstances that exist to create your problem. You mention it occurs when you hood the throttle but then mention rapidly pressing the pedal. Does it occur under a load only or will it do it in park/neutral too? Just need a little more info to clarify but to be honest if you posted over at cliffs, I have no doubt you’ll reach a resolution there.
Sorry, sort of just typed all the info out quick since it was fresh in my head. Basically if you press the pedal down, my estimation is around the 2 inch mark(about the same throttle range as if you were revving it), it will bog and if you were to hold it in this spot it could eventually kill the car. It occurs any time you give it that certain amount of throttle, but it is most noticeable when parked. Essentially it is a very large hesitation that can cause the car to die out if held in that specific zone.
Sounds like a fuel delivery or fuel mixture issue, for sure.
You say when it happens with sudden, rapid revs at idle? Sounds like your accelerator pump, which assists with fuel delivery when you give sudden revs that require a squirt of fuel to be delivered quicker than by the venturi vacuum-regulated fuel delivery increase that comes with opening the throttle plates. Make sure it's been installed correctly if it's new, and maybe replace it with one sold by Cliff Ruggles on his website that is resistant to ethanol fuels (which I'm assuming you use). Ethanol fuel swells a lot of the aftermarket accelerator pump rubber seals, rendering them useless. Textbook accelerator pump failure symptoms sound similar to what you're describing.
Another simple thing, replace your fuel filter if you haven't already. I had similar symptoms and it turned out to be a clogged fuel filter after I stuffed Berryman B12 in the gas tank... let's just stay the stuff did its job. I now routinely replace my filter every six months.
Next, are you making enough fuel pressure? Later 70's QJets with the small floats are able to easily handle 7.5 - 9.5 PSI, even according to the service manual. If you're making way less then that, you may be causing fuel starvation. Simple enough to check - swap out the fuel pump to carburetor metal line with a rubber line and tee-in a fuel pressure gauge as close to the inlet as you can, just to check your fuel pressure. After you're done, you can replace the hard line.
Three, what's your float setting at? Too low, you're starving the engine for fuel, but I doubt that it can be that low. Mine is at factory setting of 17/32 which is already super low and this issue doesn't happen to me.
Four, check allover for vacuum leaks.
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Normally Accelorator pump issues will cause an initial bog(from the momentarly lean mixture) then it'll take off and run fine when you go to WOT quickly.
Just to be clear your just starting to get into the secondaries when it happens right?
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I’m kinda having trouble understanding the circumstances that exist to create your problem. You mention it occurs when you hood the throttle but then mention rapidly pressing the pedal. Does it occur under a load only or will it do it in park/neutral too? Just need a little more info to clarify but to be honest if you posted over at cliffs, I have no doubt you’ll reach a resolution there.
Sorry, sort of just typed all the info out quick since it was fresh in my head. Basically if you press the pedal down, my estimation is around the 2 inch mark(about the same throttle range as if you were revving it), it will bog and if you were to hold it in this spot it could eventually kill the car. It occurs any time you give it that certain amount of throttle, but it is most noticeable when parked. Essentially it is a very large hesitation that can cause the car to die out if held in that specific zone.
And if you push the pedal further than that, what happens? Will the engine not die?
I tend to lean toward an accelerator pump issue as well but I’d hold off on the other stuff suggested for the time being. I don’t like introducing too many variables when troubleshooting and honestly, if it’s not dying when you press the pedal further than the point you described you’re probably not starving for fuel as far as fuel in the bowl.
You could try to record this happening. Upload a private video to YouTube and post. Don’t have to but it could speed up the diagnoses.
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I’m kinda having trouble understanding the circumstances that exist to create your problem. You mention it occurs when you hood the throttle but then mention rapidly pressing the pedal. Does it occur under a load only or will it do it in park/neutral too? Just need a little more info to clarify but to be honest if you posted over at cliffs, I have no doubt you’ll reach a resolution there.
Sorry, sort of just typed all the info out quick since it was fresh in my head. Basically if you press the pedal down, my estimation is around the 2 inch mark(about the same throttle range as if you were revving it), it will bog and if you were to hold it in this spot it could eventually kill the car. It occurs any time you give it that certain amount of throttle, but it is most noticeable when parked. Essentially it is a very large hesitation that can cause the car to die out if held in that specific zone.
Sounds like a fuel delivery or fuel mixture issue, for sure.
You say when it happens with sudden, rapid revs at idle? Sounds like your accelerator pump, which assists with fuel delivery when you give sudden revs that require a squirt of fuel to be delivered quicker than by the venturi vacuum-regulated fuel delivery increase that comes with opening the throttle plates. Make sure it's been installed correctly if it's new, and maybe replace it with one sold by Cliff Ruggles on his website that is resistant to ethanol fuels (which I'm assuming you use). Ethanol fuel swells a lot of the aftermarket accelerator pump rubber seals, rendering them useless. Textbook accelerator pump failure symptoms sound similar to what you're describing.
Another simple thing, replace your fuel filter if you haven't already. I had similar symptoms and it turned out to be a clogged fuel filter after I stuffed Berryman B12 in the gas tank... let's just stay the stuff did its job. I now routinely replace my filter every six months.
Next, are you making enough fuel pressure? Later 70's QJets with the small floats are able to easily handle 7.5 - 9.5 PSI, even according to the service manual. If you're making way less then that, you may be causing fuel starvation. Simple enough to check - swap out the fuel pump to carburetor metal line with a rubber line and tee-in a fuel pressure gauge as close to the inlet as you can, just to check your fuel pressure. After you're done, you can replace the hard line.
Three, what's your float setting at? Too low, you're starving the engine for fuel, but I doubt that it can be that low. Mine is at factory setting of 17/32 which is already super low and this issue doesn't happen to me.
Four, check allover for vacuum leaks.
Not sure if the accelerator pump I am currently using is resistant to ethanol fuel like you said but I don't see the pump you are referring to on cliffs site.
The Fuel filter is brand new and the sock inside the tank is pretty clean, I can test fuel pressure today and see check.
I replaced the float with one that come in the kit, I matched it with the factory one and I think it's sitting around 15/32. I Thought I heard 1/4 being standard in rebuilds 17 seems higher rather than lower to me but I'm not sure.
Vacuum leaks is a pretty likely thing at the moment, I am still messing with idle screws but the idle is significantly lower than when before the rebuild, I had to change idle screw a little less than a full turn. Vacuum gauge on carb manifold vacuum I get 14-15 on the gauge.
Normally Accelorator pump issues will cause an initial bog(from the momentarly lean mixture) then it'll take off and run fine when you go to WOT quickly.
Just to be clear your just starting to get into the secondaries when it happens right?
I believe its earlier than when secondary's open, if I were to accelerate normally at a stop light I would get the hesitation in first and second gear.
I’m kinda having trouble understanding the circumstances that exist to create your problem. You mention it occurs when you hood the throttle but then mention rapidly pressing the pedal. Does it occur under a load only or will it do it in park/neutral too? Just need a little more info to clarify but to be honest if you posted over at cliffs, I have no doubt you’ll reach a resolution there.
Sorry, sort of just typed all the info out quick since it was fresh in my head. Basically if you press the pedal down, my estimation is around the 2 inch mark(about the same throttle range as if you were revving it), it will bog and if you were to hold it in this spot it could eventually kill the car. It occurs any time you give it that certain amount of throttle, but it is most noticeable when parked. Essentially it is a very large hesitation that can cause the car to die out if held in that specific zone.
And if you push the pedal further than that, what happens? Will the engine not die?
I tend to lean toward an accelerator pump issue as well but I’d hold off on the other stuff suggested for the time being. I don’t like introducing too many variables when troubleshooting and honestly, if it’s not dying when you press the pedal further than the point you described you’re probably not starving for fuel as far as fuel in the bowl.
You could try to record this happening. Upload a private video to YouTube and post. Don’t have to but it could speed up the diagnoses.
If I go further on the pedal it will hesitate for a second and be fine, stomping on the pedal to WOT after the initial hesitation point won't cause any issues either. It is simply happening in this particular zone on the throttle. Yeah I can get a video it will just be hard to see, most likely later today or tomorrow.
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Zach, any chance the pull offs are not fully opening the choke?
I had a fuel supply issue on a car one time. I had to install a clear hose on the feed line to see if the pump was sucking air. Just throwing it out there as you have an interesting problem with this one.
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Played around with the car today testing stuff and I am gonna rip open the carb again if you have any ideas what I should be looking for let me know. Accelerator pump does pump gas into primaries. My most recent start up had gas spewing out of somewhere, i believe it was from the pump shaft since I don’t see gas anywhere else, funny thing is it was running really good but I realized there was gas everywhere so I shut it off. Is there a chance the accelerator pump isn’t pumping far enough into the cylandier causing it to not give me enough gas? Again, still waiting on verification on cliffs forums so I am mostly using this for documentation. Appreciate all the help so far.
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I've seen power pistons pop put of their bore and/or needle hung incorrectly on the float can cause issues but, Honestly Kinda stumped, you said you had the same problem before you rebuilt the carb right, so that tells me it's nothing you did wrong while rebuilding it.
I would check maybe power piston ear tab or arm whatever you want to call where the rods hang maybe bent. Also when the powe piston is staked in place that it moves freely should spring up and down with no effort just ligtly pushing on it.
Sorry not much help.
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Small discovery after ripping it apart again. I went to check the APT screw because I never touched it as it should be at factory settings, and it turns out it is completely bottomed out and is flush with the metal casting that the power piston pin sits on, as in the mixture is completely lean. Am I wrong that it should be roughly 3ish turns out on a 77 w72 manual, or just in any car?
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Yeah, 2~3 turns is where is should be.
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Yea, if you and stab the throttle to WOT without hesitation I’d imagine your accelerator pump is ok.
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Sorry for the language but holy doo doo^ I fixed it, I ripped the carb apart for the thousandth time and looked at the APT screw like I stated earlier, decided to take it to around a conservative 2.5 turns since I didn't want to go overboard cause I am aware of the side effects/how much tuning is required. All my issues are fixed never has it scream so loud, used a vac gauge and its around 20 made sure all the mixture screws were set right. Dad came over to see and he had an insane amount of shock, thing will rip when spring comes.
Appreciate all the responses, this forum has saved me many times.
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Awesome! Keep on keepin on man, you’re doing good!
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Small side, question what do you guys normally idle around, at the moment mine is at the 990-1050 range and feel like it is slightly too high, I think I should be aiming for 850-900. Although my idle screw on the throttle linkage is as lose as it gets so I may need to mess with the idle mixture screws to sacrifice some vacuum for lower idles, currently at 20 hgs for vacuum so I have quite a bit of head room.
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Awesome, glad you got it sorted out.
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Idling too high, start by checking to make sure the fast idle screw on the choke side isnt holding it open and the choke is fully open. Make sure the choke pulloff is working properly. You mentioned you had gas running out, was it coming out around the throttle shafts. They can wear out and let excess air in. Spray some carb cleaner around them and see what happens. Also look around for a vacuum leak somewhere, that can increase the idle speed
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Idling too high, start by checking to make sure the fast idle screw on the choke side isnt holding it open and the choke is fully open. Make sure the choke pulloff is working properly. You mentioned you had gas running out, was it coming out around the throttle shafts. They can wear out and let excess air in. Spray some carb cleaner around them and see what happens. Also look around for a vacuum leak somewhere, that can increase the idle speed
Yeah it is idling a bit too high, choke is fully open and it isn't being affected by fast idle. I can lower it to around 800 now but it isn't very reliable, if I blip the throttle it will raise RPMs but on the way down there's a good chance it will die out. Only vacuum leak that I can really think of would be either the PCV valve/grommit (it is really old) or just the carb leaking. The gas pouring out was around the accelerator pump shaft but it hasn't done that after swapping to a thicker gasket. My guess is the throttle shafts have too much play in them, I didn't do anything besides clean them, most likely need bushings.
Edit: I also should mention I have yet to put the air cleaner on and seal it off so a lot of this will more than likely change, I was just focusing on getting it running.
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Update, still losing my mind on this supposed vacuum leak. The car is running spectacular especially compared to before the rebuild, was basically missing a leg. I just know it should idle lower, idle screw is completely out and its at around 900 rpm. Sprayed carb cleaner and got no results. Gonna take a break for a few days and come back to it.
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Are you running Vacuum advance off full manifold source or ported/timed source?
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Are you running Vacuum advance off full manifold source or ported/timed source?
I believe it’s manifold, coming from passenger side TVs on the block. All lines are stock except for removing the exhaust valve and plugging that line. Set up identical to attached image.
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Did you happen to remove any of the throttle blades during your rebuild?
If you suspect a vacuum leak, while idling, place your hand over the air horn and see what happens. If your idle raises, you probably do have a vacuum leak somewhere as covering the air horn effectively richens the currently lean mixture due to the vacuum leak. If no leak, you might get a small increase but the engine should otherwise start to want to die.
Also, have you verified what your timing is set at?
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Did you happen to remove any of the throttle blades during your rebuild?
If you suspect a vacuum leak, while idling, place your hand over the air horn and see what happens. If your idle raises, you probably do have a vacuum leak somewhere as covering the air horn effectively richens the currently lean mixture due to the vacuum leak. If no leak, you might get a small increase but the engine should otherwise start to want to die.
Also, have you verified what your timing is set at?
I did not touch the throttle blades but noticed there was not any noticeable play during the rebuild, if I end up having to take the carb off again I will add bushings just incase. Placing my hand over the carb varies oddly, it was raising RPMs quite a bit initially but then I secured some things and such and it seems to be gone, now it is more likely to idle slower with my hand over the air horn but it is a very small change. Timing I will have to check tomorrow, not sure the correct wordage but last I remember it was set at 18 degrees, per factory recommendations via a light, and then the distributer was rotated and tuned by hearing a few months ago haven't touched it since rebuild.
Side note, Cliff verified me and I posted on his forums a few minutes ago so hopefully I find a solution somewhere.
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If the air horn thing is as you described you may not have a vacuum leak then. The throttle blade question was in case you removed and reinstalled the blades, you need to make sure they close tightly in the bore. The can be finicky. Ask me how I know lol. If you, or someone else didn’t, I’d hold off on bushings so as to not introduce any more variables for now.
If you say timing was set to factory 18° before too dead center (BTDC) but the timing was then adjusted by ear, I’d start back there. Verify initial timing is set at 18° at around 775 rpm (I think, don’t quote me). Vacuum advance disconnected and the vacuum line plugged. See where you end up idle wise.
Is your engine otherwise stock or does it have a different cam?
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If the air horn thing is as you described you may not have a vacuum leak then. The throttle blade question was in case you removed and reinstalled the blades, you need to make sure they close tightly in the bore. The can be finicky. Ask me how I know lol. If you, or someone else didn’t, I’d hold off on bushings so as to not introduce any more variables for now.
If you say timing was set to factory 18° before too dead center (BTDC) but the timing was then adjusted by ear, I’d start back there. Verify initial timing is set at 18° at around 775 rpm (I think, don’t quote me). Vacuum advance disconnected and the vacuum line plugged. See where you end up idle wise.
Is your engine otherwise stock or does it have a different cam?
Completely stock w72 400, I'll give the timing a shot either tomorrow or in the following days. Looks like you are correct on the factory timing specs by the way, thanks for the help so far.
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Ripped into the distributer too make sure it all looks good before I go to timing, new cap and rotor within the past 2 years. Apparently we forgot to turn 1 of the 4 screws holding it on which probably wasn't ideal. Another question, how mobile are the spinning weights supposed to be, turning the bracket below them is quite sluggish and requires quite a bit of force to make them both fully spread out, but the weights themselves move relatively smooth, but require a tiny bit of force. Just curious how much force is too much. Cleaning wise what is safe to do, they seem to be slightly rusted but no grinding or anything between the surfaces. Also after taking a look at the timing tab, it barely goes to 16 how can I reliably time to 18 degrees btdc, just eye ball it?
Thanks.
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This has now become a progress thread. Timing is set correctly and was only a degree or so off. My mind is back to vacuum leak somewhere, hand over air horn does not cause a surge but idle remains steady so air is getting somewhere. Haven't got many answers from Cliffs forum yet but someone suggested I check the throttle plates and make sure they fully close, I believe they are but I'll rip the carb off and check again.
Can anyone tell me the correct gasket order for a 1977 trans am? currently I have the metal plate on the manifold with the cylinder's walls on the plate going in towards the manifold, then the thick gasket, then the carb. This is how it came off originally, and the gasket won't fit in the reverse order.
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This has now become a progress thread. Timing is set correctly and was only a degree or so off. My mind is back to vacuum leak somewhere, hand over air horn does not cause a surge but idle remains steady so air is getting somewhere. Haven't got many answers from Cliffs forum yet but someone suggested I check the throttle plates and make sure they fully close, I believe they are but I'll rip the carb off and check again.
Can anyone tell me the correct gasket order for a 1977 trans am? currently I have the metal plate on the manifold with the cylinder's walls on the plate going in towards the manifold, then the thick gasket, then the carb. This is how it came off originally, and the gasket won't fit in the reverse order.
That is the correct order for the gasket, tin plate goes on manifold and is for EGR valve.
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Looks like it has to do with the amount of air coming through my throttle plates, Cliff suggested this too. Kind of sucks since I don't have the tools available to do it myself but I will see what I can come up with before I think about shipping it out.
Thanks again for all the help on this thread, I get a lot of my knowledge from here.
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Although I read your post on Cliffs site, I’m not a member there, so I can’t see the pictures you posted, but it sounds like the one member was suggesting adjusting the linkage first. If you’re talking about actually repositioning the throttle blades what tools are you thinking you’ll need that you’re lacking? Cliff certainly would get it done right if you sent it to him and I know he doesn’t do full rebuilds anymore but I’m not sure what he charges either.it’s not overly hard though. I rebuilt my carb and installed throttle shaft bushings. You already tore your carb apart several times so I have faith you could accomplish this.
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Although I read your post on Cliffs site, I’m not a member there, so I can’t see the pictures you posted, but it sounds like the one member was suggesting adjusting the linkage first. If you’re talking about actually repositioning the throttle blades what tools are you thinking you’ll need that you’re lacking? Cliff certainly would get it done right if you sent it to him and I know he doesn’t do full rebuilds anymore but I’m not sure what he charges either.it’s not overly hard though. I rebuilt my carb and installed throttle shaft bushings. You already tore your carb apart several times so I have faith you could accomplish this.
Yeah, I can try to adjust the linkage but my main concern is the primary throttle blades. It seems like they have quite a lot of air gaps around them and I am wondering if it will require more then just reseating the blades. I will try to fix it myself first but I might need to send it out if I can't get them perfect. I think Cliff charges 60 + I have to pay shipping.
I will attach pictures too.
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Here are the pictures. You aren't supposed to see any light, or at least very little.
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Here’s a video of mine for comparison after I reinstalled them during the bushing install. I did have to adjust them twice as I thought the first time was tight enough and now that I think about it I had an issue with it idling too high as well. . https://youtube.com/shorts/wPX6HFxdrcE?feature=share
There isn’t a lot to closing those gaps. You just have to remember those little screws have the ends smushed (I can’t remember the term off hand) to prevent them from backing out and falling down into your intake so you have to grind the end off before you remove them or they’ll likely break. Not hard to do with a dremmel. Just don’t forget to do that again with new screws.
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Honestly, dude, those air gaps look normal, assuming the throttle lever is touching your idle speed screw. You have to have them open at least a little bit for the car to run. Is that photo with your primary throttle plates COMPLETELY closed, as in, no idle speed screw limiting their travel? If so, then yes, that's too much gap - send it out to get fixed by a pro.
You may have to have your throttle plates rebushed, and honestly, like I said, I'd send the throttle plate out for that service to Cliff or maybe Mike at QuadrajetPower. If you mess it up, it's game over. It's common for quadrajets to have worn primary throttle shafts, which allows for air leaks. Secondary throttle shafts don't need to be rebushed, especially since it's important that they aren't "too tight" as to allow the large secondary butterflies to properly close. Spray some carb cleaner in those areas while the car is running and see if it changes your idle. Did you spray all around the intake to see if it causes a fluctuation in idle? Also, try opening the secondary air valves while at idle and see if that makes a change - and by air valve, I mean the ones at the top you can actually see and are opened by vacuum. While at idle speed, if you manually push down the secondary air valves, it shouldn't make any difference in idle since the secondaries should be fully closed tight. If there is a change in idle speed, then the issue is with your secondary throttle plates not fully seating closed.
Also, what emissions equipment are you using? If all your emissions crap is still hooked up and your car is running hot, there is a very remote possibility that your DS-TVS is adding timing to your idle like it's designed to do when the sensor detects a coolant temp of around 205+. By adding timing, it speeds up the idle, therefore water pump circulation - plus, more timing at idle typically makes the car run cooler. This is very unlikely and would only make sense if you're running hot while the idle is high, and you have all your emissions equipment hooked up.
Finally, what tension springs do you have in your distributor? If you have those crapola "light" springs (usually copper in color) out of those recurve kits, it's possible that you're adding timing at idle that you shouldn't be adding. Stock distributor springs are usually very heavy and stiff as to prevent this - as in, when you rev up the engine and return to idle, it returns to where it should. If the springs are too light, you'll create a positive feedback loop that ends up raising your idle speed once you rev up the motor. The point of those light springs is to have your mechanical advance come in early for performance, but they're not very practical for street-driven cars. The ONLY timing that should be present at idle is your base timing setting (which for your W72 should be 18 degrees BTDC), which is set WITHOUT VACUUM ADVANCE, and then your vacuum advance on top of that if you're using manifold vacuum. And you need a timing light to correctly set timing.
One more thing - the only reason you're making that healthy 20 or so inches of vacuum at idle is BECAUSE you're idling so high. Once you get your idle down to a reasonable level, you'll probably end up seeing 16-17" on the vac gauge, which is still perfectly healthy.
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Your APT setting should be bottom out then 1.5-2 turns up. Sounds like you found it though.
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Interesting thread. Seems like it's staggent right now, but think I'll toss in my 2 cents. (Is there a "cents" symbol on these keys? I don't see one)
Anyway, most will tell you, when a QJ is operating/idling correctly, the throttle blades are suppose to be in the middle of the part throttle slots in the base plates. there is some wiggle room, but if your blades are "above" those slots, you could get a temporary bog, hi idle, and possibly even some nozzle drip.
I was able to fix a nozzle drip from a Chevy carb I did for my warmed over 428 many years ago. Went deep into the carb to cure the drip, and ended up changing to an entirely different carb that had air idle bypass. No matter how much I lowered the mech. throttle screw to close off the air, (on the 1st QJ), the car would run like crap. Even tried drilling holes in the plates, (which did nothing more than aggravate the drip). Once I ripped the guts out of it, and installed them into the other carb, problem solved. Could even get it to idle down as low as 600, with the 041 cam. (I miss that eng., and carb)
Not saying this is relevant to you, and by the photos above, it looks like your blades are positioned OK, at least from the angle I'm looking at. Just something to consider when troubleshooting. Good job so far. Wondering how much help Cliff has been? i hear he's a busy guy.
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Interesting thread. Seems like it's staggent right now, but think I'll toss in my 2 cents. (Is there a "cents" symbol on these keys? I don't see one)
Anyway, most will tell you, when a QJ is operating/idling correctly, the throttle blades are suppose to be in the middle of the part throttle slots in the base plates. there is some wiggle room, but if your blades are "above" those slots, you could get a temporary bog, hi idle, and possibly even some nozzle drip.
I was able to fix a nozzle drip from a Chevy carb I did for my warmed over 428 many years ago. Went deep into the carb to cure the drip, and ended up changing to an entirely different carb that had air idle bypass. No matter how much I lowered the mech. throttle screw to close off the air, (on the 1st QJ), the car would run like crap. Even tried drilling holes in the plates, (which did nothing more than aggravate the drip). Once I ripped the guts out of it, and installed them into the other carb, problem solved. Could even get it to idle down as low as 600, with the 041 cam. (I miss that eng., and carb)
Not saying this is relevant to you, and by the photos above, it looks like your blades are positioned OK, at least from the angle I'm looking at. Just something to consider when troubleshooting. Good job so far. Wondering how much help Cliff has been? i hear he's a busy guy.
Thread is currently dead cause of procrastination and shipping. Took me a week to send out the carb, Cliff fixed it up real quick and has been very responsive, shipping is currently taking longer than his labor. Carb should be hear in the next day or so then I'll see what progress that made. Another thing that I need to check more thoroughly is the intake manifold gasket but don't want to take that apart unless I need to.
Your APT setting should be bottom out then 1.5-2 turns up. Sounds like you found it though.
Yep, figured my carb was untouched prior to our ownership but no ones ever seen an APT screw bottomed out on a factory carb. I brought it up 2.5ish turns and it immediately ran better and had no more bogging on acceleration, was my whole issue. After I fix the carb I will most likely tap the plug and do more APT adjusting.
Honestly, dude, those air gaps look normal, assuming the throttle lever is touching your idle speed screw. You have to have them open at least a little bit for the car to run. Is that photo with your primary throttle plates COMPLETELY closed, as in, no idle speed screw limiting their travel? If so, then yes, that's too much gap - send it out to get fixed by a pro.
You may have to have your throttle plates rebushed, and honestly, like I said, I'd send the throttle plate out for that service to Cliff or maybe Mike at QuadrajetPower. If you mess it up, it's game over. It's common for quadrajets to have worn primary throttle shafts, which allows for air leaks. Secondary throttle shafts don't need to be rebushed, especially since it's important that they aren't "too tight" as to allow the large secondary butterflies to properly close. Spray some carb cleaner in those areas while the car is running and see if it changes your idle. Did you spray all around the intake to see if it causes a fluctuation in idle? Also, try opening the secondary air valves while at idle and see if that makes a change - and by air valve, I mean the ones at the top you can actually see and are opened by vacuum. While at idle speed, if you manually push down the secondary air valves, it shouldn't make any difference in idle since the secondaries should be fully closed tight. If there is a change in idle speed, then the issue is with your secondary throttle plates not fully seating closed.
Also, what emissions equipment are you using? If all your emissions crap is still hooked up and your car is running hot, there is a very remote possibility that your DS-TVS is adding timing to your idle like it's designed to do when the sensor detects a coolant temp of around 205+. By adding timing, it speeds up the idle, therefore water pump circulation - plus, more timing at idle typically makes the car run cooler. This is very unlikely and would only make sense if you're running hot while the idle is high, and you have all your emissions equipment hooked up.
Finally, what tension springs do you have in your distributor? If you have those crapola "light" springs (usually copper in color) out of those recurve kits, it's possible that you're adding timing at idle that you shouldn't be adding. Stock distributor springs are usually very heavy and stiff as to prevent this - as in, when you rev up the engine and return to idle, it returns to where it should. If the springs are too light, you'll create a positive feedback loop that ends up raising your idle speed once you rev up the motor. The point of those light springs is to have your mechanical advance come in early for performance, but they're not very practical for street-driven cars. The ONLY timing that should be present at idle is your base timing setting (which for your W72 should be 18 degrees BTDC), which is set WITHOUT VACUUM ADVANCE, and then your vacuum advance on top of that if you're using manifold vacuum. And you need a timing light to correctly set timing.
One more thing - the only reason you're making that healthy 20 or so inches of vacuum at idle is BECAUSE you're idling so high. Once you get your idle down to a reasonable level, you'll probably end up seeing 16-17" on the vac gauge, which is still perfectly healthy.
Yep, completely closed. Sent it out to cliff since he has a pretty solid price and I'd rather not accidentally wreck mine. I checked for vacuum leaks with carb cleaner but didn't do manifold thoroughly that could still be a variable. From memory I don't think the secondaries had any affect on idle when manually opening them. I still have all the factory emissions stuff hooked up except the exhaust valve, vacuum line plugged. I have a real nice aluminum rad from a friend, car never goes over 180ish?, what ever the 1/4 line is on the gauge. Distributer has stock springs and weights, cleaned them up during this session, they seem to be pretty stiff and heavy, not light. Timing was set correctly. Yeah, was slow on realizing vacuum is correlated to RPM but I figured it out quickly after my first messages.
Carb will be here in a few days and I will post another update, appreciate all the help and info.
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Great thread, I don't do carbs, mine was done by a local guy I know but this sure was an interesting read. Glad to see your probably on the other side of this issue Zach. Can be very frustrating trying to figure out these gremlins.
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Well, I got the carb back today and throttle shaft is a lot more solid.
Issue still remains, no change in performance from before and after the rebuild. I have a vacuum leak somewhere and I cannot find it. Putting my hand over the primaries and completely suffocating it causes no change in idle speed or anything noticeable. Curb idle screw completely out, idle mixture screws set to best I can get at the moment 3ish turns out. Making around 16ish vacuum at 1000 rpm. Only places I can think of are bad gaskets on the carb, they are brand new. Brake booster, brand new, but I can try disconnecting it from the vacuum and plugging it. Intake manifold gasket has been on there for a while, I can try spraying more carb cleaner later. Spraying carb cleaner anywhere else doesn't reveal anything, I've replace most things on it, vacuum lines, PCV valve, etc. not sure what else to do. Could the APT screw cause a higher idle? It was bottomed out so I am unsure where it is supposed to be, did 2.5ish turns and it fixed my original acceleration issue but I am wondering if it needs tuning for idle or if its only for cruising air/fuel.
Just a bit annoyed, going on vacation to the Dominican in a few days so I wont be able to test anything. I appreciate all the help so far.
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Well, I got the carb back today and throttle shaft is a lot more solid.
Issue still remains, no change in performance from before and after the rebuild. I have a vacuum leak somewhere and I cannot find it. Putting my hand over the primaries and completely suffocating it causes no change in idle speed or anything noticeable. Curb idle screw completely out, idle mixture screws set to best I can get at the moment 3ish turns out. Making around 16ish vacuum at 1000 rpm. Only places I can think of are bad gaskets on the carb, they are brand new. Brake booster, brand new, but I can try disconnecting it from the vacuum and plugging it. Intake manifold gasket has been on there for a while, I can try spraying more carb cleaner later. Spraying carb cleaner anywhere else doesn't reveal anything, I've replace most things on it, vacuum lines, PCV valve, etc. not sure what else to do. Could the APT screw cause a higher idle? It was bottomed out so I am unsure where it is supposed to be, did 2.5ish turns and it fixed my original acceleration issue but I am wondering if it needs tuning for idle or if its only for cruising air/fuel.
Just a bit annoyed, going on vacation to the Dominican in a few days so I wont be able to test anything. I appreciate all the help so far.
:shock:You,ve gutta be kidding? You're telling us, when the eng. is warmed, you can completely shut your choke blade, and it won't load up and stall?
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Well, I got the carb back today and throttle shaft is a lot more solid.
Issue still remains, no change in performance from before and after the rebuild. I have a vacuum leak somewhere and I cannot find it. Putting my hand over the primaries and completely suffocating it causes no change in idle speed or anything noticeable. Curb idle screw completely out, idle mixture screws set to best I can get at the moment 3ish turns out. Making around 16ish vacuum at 1000 rpm. Only places I can think of are bad gaskets on the carb, they are brand new. Brake booster, brand new, but I can try disconnecting it from the vacuum and plugging it. Intake manifold gasket has been on there for a while, I can try spraying more carb cleaner later. Spraying carb cleaner anywhere else doesn't reveal anything, I've replace most things on it, vacuum lines, PCV valve, etc. not sure what else to do. Could the APT screw cause a higher idle? It was bottomed out so I am unsure where it is supposed to be, did 2.5ish turns and it fixed my original acceleration issue but I am wondering if it needs tuning for idle or if its only for cruising air/fuel.
Just a bit annoyed, going on vacation to the Dominican in a few days so I wont be able to test anything. I appreciate all the help so far.
Don't mean to sound coy on this but, are all the vaccuum connections on the carb plugged or have a hose attached? I know one of my front vacuum inlets on the carb had a "cover" or plug over it so it didn't leak until I properly attached it. I'm just trying to think outside the box.
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Well, I got the carb back today and throttle shaft is a lot more solid.
Issue still remains, no change in performance from before and after the rebuild. I have a vacuum leak somewhere and I cannot find it. Putting my hand over the primaries and completely suffocating it causes no change in idle speed or anything noticeable. Curb idle screw completely out, idle mixture screws set to best I can get at the moment 3ish turns out. Making around 16ish vacuum at 1000 rpm. Only places I can think of are bad gaskets on the carb, they are brand new. Brake booster, brand new, but I can try disconnecting it from the vacuum and plugging it. Intake manifold gasket has been on there for a while, I can try spraying more carb cleaner later. Spraying carb cleaner anywhere else doesn't reveal anything, I've replace most things on it, vacuum lines, PCV valve, etc. not sure what else to do. Could the APT screw cause a higher idle? It was bottomed out so I am unsure where it is supposed to be, did 2.5ish turns and it fixed my original acceleration issue but I am wondering if it needs tuning for idle or if its only for cruising air/fuel.
Just a bit annoyed, going on vacation to the Dominican in a few days so I wont be able to test anything. I appreciate all the help so far.
:shock:You,ve gutta be kidding? You're telling us, when the eng. is warmed, you can completely shut your choke blade, and it won't load up and stall?
Well, I might’ve been doing the hand test a bit wrong. Choke completely shut, engine runs and doesn’t stumble, and hand over same thing. Although if I smash my hand and completely suffocate it it will die, I’ve been laying my hand over the primaries, it only dies if I force my hand a bit and feel the vacuum pull on my hand. Wondering if I’ve been doing this wrong the entire time.
Well, I got the carb back today and throttle shaft is a lot more solid.
Issue still remains, no change in performance from before and after the rebuild. I have a vacuum leak somewhere and I cannot find it. Putting my hand over the primaries and completely suffocating it causes no change in idle speed or anything noticeable. Curb idle screw completely out, idle mixture screws set to best I can get at the moment 3ish turns out. Making around 16ish vacuum at 1000 rpm. Only places I can think of are bad gaskets on the carb, they are brand new. Brake booster, brand new, but I can try disconnecting it from the vacuum and plugging it. Intake manifold gasket has been on there for a while, I can try spraying more carb cleaner later. Spraying carb cleaner anywhere else doesn't reveal anything, I've replace most things on it, vacuum lines, PCV valve, etc. not sure what else to do. Could the APT screw cause a higher idle? It was bottomed out so I am unsure where it is supposed to be, did 2.5ish turns and it fixed my original acceleration issue but I am wondering if it needs tuning for idle or if its only for cruising air/fuel.
Just a bit annoyed, going on vacation to the Dominican in a few days so I wont be able to test anything. I appreciate all the help so far.
Don't mean to sound coy on this but, are all the vaccuum connections on the carb plugged or have a hose attached? I know one of my front vacuum inlets on the carb had a "cover" or plug over it so it didn't leak until I properly attached it. I'm just trying to think outside the box.
Hey I’ll take any advice, I believe everything is plugged and connected sufficiently I replace a lot of hoses and plugs. One thing I still need to try is unplug all vacuum lines and plug them to see if it’s a random vacuum device leaking.
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This thread was locked for some reason, I wonder if I tapped it by accident. Anyways I did some more playing around, high idle cam was hitting a small bit but I fixed that, but it didn't solve any issues. I think I'm past vacuum leaks, hand over carb does in fact kill it. Now I am wondering if it is a timing issue, still set to 18 BTDC at 1k rpm using the factory vacuum line routes, manifold vacuum from carb through the emissions check valve. Or something is wrong with my idle circuit and it is dumping too much fuel or air. It was a stock rebuild and clean, I didn't add any hop ups, like jets, or idle bypass, etc. Just to restate it, curb idle screw can be completely unscrewed (transfer slot can only be seen a little bit), and the car will still run at 1k rpm 18 vacuum pretty steady.
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DO you have a bit of slack in the throttle cable and trans kickdown cables. Could they be holding it slightly open. Still sounds like a vacuum leak somewhere. Try unhooking all the lines and capping off all ports. Make sure PCV valve is clean. They are designed to let a metered amount of air thru them at idle. If the valve is hanging slightly open it can let an excessive amount of air through. It wouldn't take much to effect the idle.
You mentioned earlier the distributor weights were sluggish. I had to remove my distributor and clean the inner shaft to loosen it up. Years of crud had made it almost inoperative. The weights could work their way out but the springs didnt have enough force to pull them back in fully. Once the shafts had been cleaned and lubed everything worked as it should. You could pull the weights apart and they would snap back in place when released. Now thinking about it, seems like I was having problems with a high idle when I found this.
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DO you have a bit of slack in the throttle cable and trans kickdown cables. Could they be holding it slightly open. Still sounds like a vacuum leak somewhere. Try unhooking all the lines and capping off all ports. Make sure PCV valve is clean. They are designed to let a metered amount of air thru them at idle. If the valve is hanging slightly open it can let an excessive amount of air through. It wouldn't take much to effect the idle.
You mentioned earlier the distributor weights were sluggish. I had to remove my distributor and clean the inner shaft to loosen it up. Years of crud had made it almost inoperative. The weights could work their way out but the springs didnt have enough force to pull them back in fully. Once the shafts had been cleaned and lubed everything worked as it should. You could pull the weights apart and they would snap back in place when released. Now thinking about it, seems like I was having problems with a high idle when I found this.
Just have a throttle cable and no, taking the carb off the car I can physically see where the throttle blades are relative to the curb idle screw so I know for the fact they are completely shut or near completely shut (slightly open for a square transfer slot). PCV valve is brand new and the ball rattles around, I need to replace the valley pan gasket but I need the intake off to make that not a huge pain, it is in good enough shape to not cause a leak. Unhooking the PCV valve and plugging it causes no change besides pushing smoke through the air valve covers to the air cleaner. I can take a closer look at the weights and springs again, did a quick check and rubbed them down and cleaned them a tiny bit, didn't feel sticky just really strong but smooth.
Something that is now in my mind is that, I know for a fact the throttle blades are completely closed and were check by Cliff, IF I have a vacuum leak it has to come from below that, which only leaves, carb base gasket, carb flange gasket, intake manifold, and the little hole that transfers hot air below the carb. I sprayed a lot of carb cleaner around the base so I believe I can eliminate any fitment or gasket issues. Not sure the best way to check for intake manifold leaks, I sprayed carb cleaner around the right and left side and noticed no rpm change. One thing that I am not sure about is the emissions air passage that pushes air below carb through the manifold, this could be not working correctly, I don't have much information on it so this is a unknown area for me and I am not sure how to test it. Or the metal flange gasket I have for the carb is wrong, it was on the car when I took the carb off but I learned the carb was touched with before our ownership so I can't guarantee it is correct.
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DO you have a bit of slack in the throttle cable and trans kickdown cables. Could they be holding it slightly open. Still sounds like a vacuum leak somewhere. Try unhooking all the lines and capping off all ports. Make sure PCV valve is clean. They are designed to let a metered amount of air thru them at idle. If the valve is hanging slightly open it can let an excessive amount of air through. It wouldn't take much to effect the idle.
You mentioned earlier the distributor weights were sluggish. I had to remove my distributor and clean the inner shaft to loosen it up. Years of crud had made it almost inoperative. The weights could work their way out but the springs didnt have enough force to pull them back in fully. Once the shafts had been cleaned and lubed everything worked as it should. You could pull the weights apart and they would snap back in place when released. Now thinking about it, seems like I was having problems with a high idle when I found this.
Just have a throttle cable and no, taking the carb off the car I can physically see where the throttle blades are relative to the curb idle screw so I know for the fact they are completely shut or near completely shut (slightly open for a square transfer slot). PCV valve is brand new and the ball rattles around, I need to replace the valley pan gasket but I need the intake off to make that not a huge pain, it is in good enough shape to not cause a leak. Unhooking the PCV valve and plugging it causes no change besides pushing smoke through the air valve covers to the air cleaner. I can take a closer look at the weights and springs again, did a quick check and rubbed them down and cleaned them a tiny bit, didn't feel sticky just really strong but smooth.
Something that is now in my mind is that, I know for a fact the throttle blades are completely closed and were check by Cliff, IF I have a vacuum leak it has to come from below that, which only leaves, carb base gasket, carb flange gasket, intake manifold, and the little hole that transfers hot air below the carb. I sprayed a lot of carb cleaner around the base so I believe I can eliminate any fitment or gasket issues. Not sure the best way to check for intake manifold leaks, I sprayed carb cleaner around the right and left side and noticed no rpm change. One thing that I am not sure about is the emissions air passage that pushes air below carb through the manifold, this could be not working correctly, I don't have much information on it so this is a unknown area for me and I am not sure how to test it. Or the metal flange gasket I have for the carb is wrong, it was on the car when I took the carb off but I learned the carb was touched with before our ownership so I can't guarantee it is correct.
Wouldn't be the hot air choke passage since that's a calibrated vacuum leak thats meant to be there. In fact, that's how the later carbs get their air bypass, rather than drilled into the baseplate like the earlier carbs.
Just spit-ballin' here, but does that 1000 RPM actually sound and feel like 1000 RPM, or are you just looking at the factory tach? I had a "high idle" issue for a long time that only happened after I cruised for a bit in 4th gear... it would return to a higher idle than what I set it at, but lo and behold, I hooked up a Unova timing light with an RPM display and verified that I was actually idling where I should be, and that the factory tach was off. These days I just look at my oil pressure gauge to verify I'm at idle when I'm warmed up. 750 RPM reads dead center ar 40 PSI at operating temp.
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DO you have a bit of slack in the throttle cable and trans kickdown cables. Could they be holding it slightly open. Still sounds like a vacuum leak somewhere. Try unhooking all the lines and capping off all ports. Make sure PCV valve is clean. They are designed to let a metered amount of air thru them at idle. If the valve is hanging slightly open it can let an excessive amount of air through. It wouldn't take much to effect the idle.
You mentioned earlier the distributor weights were sluggish. I had to remove my distributor and clean the inner shaft to loosen it up. Years of crud had made it almost inoperative. The weights could work their way out but the springs didnt have enough force to pull them back in fully. Once the shafts had been cleaned and lubed everything worked as it should. You could pull the weights apart and they would snap back in place when released. Now thinking about it, seems like I was having problems with a high idle when I found this.
Just have a throttle cable and no, taking the carb off the car I can physically see where the throttle blades are relative to the curb idle screw so I know for the fact they are completely shut or near completely shut (slightly open for a square transfer slot). PCV valve is brand new and the ball rattles around, I need to replace the valley pan gasket but I need the intake off to make that not a huge pain, it is in good enough shape to not cause a leak. Unhooking the PCV valve and plugging it causes no change besides pushing smoke through the air valve covers to the air cleaner. I can take a closer look at the weights and springs again, did a quick check and rubbed them down and cleaned them a tiny bit, didn't feel sticky just really strong but smooth.
Something that is now in my mind is that, I know for a fact the throttle blades are completely closed and were check by Cliff, IF I have a vacuum leak it has to come from below that, which only leaves, carb base gasket, carb flange gasket, intake manifold, and the little hole that transfers hot air below the carb. I sprayed a lot of carb cleaner around the base so I believe I can eliminate any fitment or gasket issues. Not sure the best way to check for intake manifold leaks, I sprayed carb cleaner around the right and left side and noticed no rpm change. One thing that I am not sure about is the emissions air passage that pushes air below carb through the manifold, this could be not working correctly, I don't have much information on it so this is a unknown area for me and I am not sure how to test it. Or the metal flange gasket I have for the carb is wrong, it was on the car when I took the carb off but I learned the carb was touched with before our ownership so I can't guarantee it is correct.
Wouldn't be the hot air choke passage since that's a calibrated vacuum leak thats meant to be there. In fact, that's how the later carbs get their air bypass, rather than drilled into the baseplate like the earlier carbs.
Just spit-ballin' here, but does that 1000 RPM actually sound and feel like 1000 RPM, or are you just looking at the factory tach? I had a "high idle" issue for a long time that only happened after I cruised for a bit in 4th gear... it would return to a higher idle than what I set it at, but lo and behold, I hooked up a Unova timing light with an RPM display and verified that I was actually idling where I should be, and that the factory tach was off. These days I just look at my oil pressure gauge to verify I'm at idle when I'm warmed up. 750 RPM reads dead center ar 40 PSI at operating temp.
Actually thought about hooking up another tac cause I’m not sure what 1000 rpm feels like compared to lower rpm’s on the car since it’s never idled low. But shouldn’t the car still want to die if the curb idle screw is all the way out, makes me think there is still an issue somewhere. I can only test idle in neutral since Minnesota is currently covered in snow. Oil pressure jitters around 40.
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Does the car creep in gear, if you take your foot off the gas? Is your converter stock?
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Does the car creep in gear, if you take your foot off the gas? Is your converter stock?
I should clarify it is a manual 4 speed transmission everything is stock, but the car will move without the gas pedal into 1st and cruise relatively quickly, another reason why I believe the current tac to be accurately showing 1k rpm.
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You mentioned the carb had been worked on before you got the car. Could it be possible its not the original carb. Reason im asking is I have 2 different carbs that came off my brother in laws 82 corvette w/a 350. I tried them both on my 305 and couldn't get either one to idle down. The idle screws were backed off to not touch on either one. I don't know for sure but I suspect the factory had them calibrated the idle flow air for the later smog engine they were designed for. I've also got older carbs that will idle down but not these.
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You mentioned the carb had been worked on before you got the car. Could it be possible its not the original carb. Reason im asking is I have 2 different carbs that came off my brother in laws 82 corvette w/a 350. I tried them both on my 305 and couldn't get either one to idle down. The idle screws were backed off to not touch on either one. I don't know for sure but I suspect the factory had them calibrated the idle flow air for the later smog engine they were designed for. I've also got older carbs that will idle down but not these.
Pretty confident it is the original or at least a stock replacement, carb number matches the car, year, Pontiac, manual, etc and is the performance 800 cfm with the vent that was specifically made for performance Pontiac engines. In terms of what they messed with I am unsure but Cliff said he’s never seen a bottomed APT screw from factory, everything else inside the carb is stock I didn’t notice any other signs.
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Well spent a week scouring the web for anything relating to high idle and can’t find anything that has helped so far, if it is a vacuum leak I cannot find where it coming from, carb runs the same with vacuum lines plugged, brake booster, pcv, etc. vacuum advance has no change at idle from what I can tell. However there is an oddity that it will run around 800 rpm just fine but has a slight hesitation, cannot reproduce it, happened after reconnecting all vacuum lines but it eventually builds rpm and stays at 1k, I’m wondering if the vac advance is sticking or it’s something distributer wise. Throttle linkage cannot be physically more closed.
Currently fighting below freezing temps so I might post pone this issue until summer, car will still run great it just has a slight idle issue.
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If your vac. adv. is stock, then it will be ported at the carb., (no vacuum). And the idle won't change when disconnected. But if you've hooked it up to manifold vac., then the idle should go down, when disconnected. Engs. run so much better when vacuum is hooked to the canister at idle. They run smoother, cooler, better mileage, and snappier throttle response.
As you probably know, when you set your initial timing, you plug the canister, and adj., then hook the vacuum back up. RPMs should increase if you're hooked to manifold vac. If this doesn't happen, either the canister is leaking internally, or maybe your mech. weights are stuck. (Just some more food for thought(. Keep at it. Depending on your cam, you should be able to idle at 700. Not sure if you mentioned the car creeping when idling.
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If your vac. adv. is stock, then it will be ported at the carb., (no vacuum). And the idle won't change when disconnected. But if you've hooked it up to manifold vac., then the idle should go down, when disconnected. Engs. run so much better when vacuum is hooked to the canister at idle. They run smoother, cooler, better mileage, and snappier throttle response.
As you probably know, when you set your initial timing, you plug the canister, and adj., then hook the vacuum back up. RPMs should increase if you're hooked to manifold vac. If this doesn't happen, either the canister is leaking internally, or maybe your mech. weights are stuck. (Just some more food for thought(. Keep at it. Depending on your cam, you should be able to idle at 700. Not sure if you mentioned the car creeping when idling.
I can hook up manifold vacuum just to test for leaks, last time I opened distributer mech seemed to move fine and required a bit of force, tested vac adv with a vacuum gun and it seemed to operate fine. yeah stock spec is 775 rpm and I can't even get down to there. The times the car has idled at 800 it was stable but I can't reproduce it, so it isn't like it is dying just can't figure out what is causing the high rpms. Also not sure the definition of creep in terms of a manual car.
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Oops, sorry Zach, I keep forgetting your a stick. Won't be creeping with that. I think someone mentioned the accuracy of your tach. I'm sure you've already double checked that.
You've said the car runs fine, just idles higher than you think it should. You've also said your mech. idle screw is cranked all the way out. With a Cliff R carb. rebuilt, the initial timing set correctly, the curb idle screw taken out, and no vacuum leaks, it sure seems strange it won't go down. Is there a way you could post a quick video of it iding, with an underhood shot for about 30 sec, (with a couple quick revs,), and then a shot of it from the rear, to hear the exhaust? Sure would help here.
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Oops, sorry Zach, I keep forgetting your a stick. Won't be creeping with that. I think someone mentioned the accuracy of your tach. I'm sure you've already double checked that.
You've said the car runs fine, just idles higher than you think it should. You've also said your mech. idle screw is cranked all the way out. With a Cliff R carb. rebuilt, the initial timing set correctly, the curb idle screw taken out, and no vacuum leaks, it sure seems strange it won't go down. Is there a way you could post a quick video of it iding, with an underhood shot for about 30 sec, (with a couple quick revs,), and then a shot of it from the rear, to hear the exhaust? Sure would help here.
Yeah for sure I can do a video, just set the APT screw to be more lean to test it out and got rewarded with a volcano of gas and a no start issues so once I sort that sorted out I can get a video in a day or so. Got a new timing light with rpm so I will verify that issue before too.
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Going to post a long status update, to sum it up 99% chance that it is fixed.
Opened up the carb and set the APT screw to around 3 turns instead of 2, shouldn't affect idle but I was willing to try everything. Reset my float height cause I was dealing with flooding every time I took the carb on and off the manifold, issue fixed. Ordered 2 new thick air horn gaskets cause I broke the two that I had since I have opened my carb 50 times, one I have is good enough but should be replaced. Found the vacuum hose going from the charcoal canister to the fuel tank to be pretty rotted seemed to still be a solid connection but I wasn't taking chances. Started up the car everything was running great however my tach was still reading 1000 ish once the choke opened and was warm. I wanted to check if my tach was right so I went and bought a fancy timing light from hobo freight that shows rpm and all that, hooked it up and lo and behold it is starting my tach is ready around 300 rpm high and doesn't want to drop below 1000 rpm. Did a bunch of timing work and got to around 18 degrees at 750 rpm, which is really close to factory settings. I seem to have a bit of vacuum/ rpm fluctation, 0-50rpm / 0-0.5 vacuum, might need to adjust mixture screws but I am gonna wait till spring for that. Car seems to be running great, I am unsure what the car is supposed to sound like at 750 rpm since my tach never read right, but I am willing to believe my timing light. As nuclear said 40 psi of oil pressure around 800 is accurate and that is what I am getting. A new issue arose with starting after being hot, but that is for another thread. After all of this my issues ranged from vacuum leaks, throttle blades, wrong settings within carb, and a heck of a lot of other stuff. It is strange my tach reads wrong though? Anyone have any idea for that?
Appreciate everyone in here for the help, I think I am finally finished for carb work besides a small amount of tuning. Wouldn't of got solved this issues without this forum, there is only so much information out there and it is pretty hard to find. Thanks again!
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Can't say I am thrilled, first day I was able to take the trans am out and it didn't run great at all. Car starts up cold or hot just fine and revs fine around 40 degrees out, no issues in the garage. Once I take it out on the road I notice a lot of hesitation as if I am running out of gas, when ever I try accelerating it likes to fall flat and not build RPMs and stutter. I notice it starts running slightly better as I am driving around and heat up the engine but this is after 20+ mins of running and getting gas a mile away, I believe the choke is working as it should and I don't see why it would cause the car to act this way. Once everything gets hot, choke is way past being off by now, the car starts to build idle RPMs to around 1100, if i accelerate it builds rpms fine but takes a significant amount of time to drop back down. Any ideas on what to check? Gonna post over at Cliffs as well.
I suspect it is running lean but unsure what to change.
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I no carb expert but that sounds rich to me. May be worth it to get a oxygen sensor/meter to see what is really going on there.
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I no carb expert but that sounds rich to me. May be worth it to get a oxygen sensor/meter to see what is really going on there.
No carb expert here either I can just google things fast, from my research I thought it was a lean surge, I would expect black smoke if it was running this rich. Although not sure symptoms of a rich quadrajet. I am going to mess with the APT screw and richen it a bit to see, never tuned it.
I am thinking the TVS valve that adds timing when engine is hot is my suspect for increased RPM although I don't remember running hot, I have a large aluminum rad that keeps the temp steady at what ever the quarter mark is on the gauge, 190?
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Going to summarize my main issue a bit fr after fiddling around with it, idle is great and revving in neutral is great, under load coming off idle, part throttle, and WOT, causes a bog/bucking acceleration, it will accelerate and open the secondaries but it is slow and bucks lightly. Adjusted the APT screw from 3.5 turns out - 4, small change I think, 4 - 4.5, no noticeable change.
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It sure sounds like there may be other problems with this engine beyond carb. issues. Checking for a mechanically sound long block might be a good idea. A leak down test of each cylinder is a good place to start. Every cylinder needs a good valve and ring seal. A broken top ring can act real weird, seeming OK on a compression test, but fail a leak down. It can make low load driving symptoms similar to what you are describing while seeming normal at WOT. Compression entering the intake or exhaust while testing can reveal valve lash issues or burnt valve and seats or even carbon build up that is keeping them from sealing. The tools are not expensive and the time is worth it, if it keeps you from going in circles with an issue. How is the timing chain? Again, a simple test by rotating the crank one direction by hand and watching the rotor and reversing the direction to be sure the rotor moves as soon as the crank moves will reveal any wear. If it lags, it is worn. Too much wear and it may have jumped a tooth. Again, simple test that can help prevent wasted time. Once it is certain that the long block is sound, then distributor and carburetor operation and tuning should be addressed, and with both the devil is in the details.
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It sure sounds like there may be other problems with this engine beyond carb. issues. Checking for a mechanically sound long block might be a good idea. A leak down test of each cylinder is a good place to start. Every cylinder needs a good valve and ring seal. A broken top ring can act real weird, seeming OK on a compression test, but fail a leak down. It can make low load driving symptoms similar to what you are describing while seeming normal at WOT. Compression entering the intake or exhaust while testing can reveal valve lash issues or burnt valve and seats or even carbon build up that is keeping them from sealing. The tools are not expensive and the time is worth it, if it keeps you from going in circles with an issue. How is the timing chain? Again, a simple test by rotating the crank one direction by hand and watching the rotor and reversing the direction to be sure the rotor moves as soon as the crank moves will reveal any wear. If it lags, it is worn. Too much wear and it may have jumped a tooth. Again, simple test that can help prevent wasted time. Once it is certain that the long block is sound, then distributor and carburetor operation and tuning should be addressed, and with both the devil is in the details.
Will definitely do at some point however it has 70k miles and was running strong pre carb besides some bad carb issues. The extra timing I am going to blame on the TVS emission plug, I don’t remember what the temp was at but it hasn’t happened since I corrected my timing and idle. Need to test for 0 degrees I don’t think my timing makes are correct. Secondary air valves were also too loose and dramatically helped although wasn’t able to finish yesterday. Changed oil yesterday as well and it was looking pretty good.
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I am gonna say it is a timing issue, not sure if my timing marks are correct on the harmonic though. It runs significantly better when there is more timing 14-18 initial (factory) however my starter does not like it. 8 degrees initial is the absolute highest I can go in order for a smoothish crank on the starter. Currently in a decent spot but I know there is more power. I would run a high timing but I don't want to starter to constantly fail on me. The start issue only occurs when the engine is hot however. Maybe I can wrap it and see, don't have materials on hand for that at the moment though. Any ideas?
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Again, I'm not a good carb guy but maybe try removing the vacuum line to the brake booster and plugging it. Just to make sure it isn't sucking air there. Also double check with some brake cleaner or something that there isn't some crazy vacuum leak where the carb attaches.
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8* initial is not enough timing for these engines14* degrees should not be so much timing that the starter hard starts. I could see and have experience 18*. I've wrapped my starter solenoid with heat reflective tape and a put a heat shield, didn't make a dam difference, heat and old wires don't get along either check your main battery cable, and red wire going to the solenoid some guys also install Ford type solenoids. Or high torque mini starters. Problem with installing high torque mini starter is there several measurements and things to check before slapping it on but with 4 speeds bellhousing you can't gain enough access to measure properly without removing it.
Hot start issues is not uncommon for Pontiac's unfortunately.
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8* initial is not enough timing for these engines14* degrees should not be so much timing that the starter hard starts. I could see and have experience 18*. I've wrapped my starter solenoid with heat reflective tape and a put a heat shield, didn't make a dam difference, heat and old wires don't get along either check your main battery cable, and red wire going to the solenoid some guys also install Ford type solenoids. Or high torque mini starters. Problem with installing high torque mini starter is there several measurements and things to check before slapping it on but with 4 speeds bellhousing you can't gain enough access to measure properly without removing it.
Hot start issues is not uncommon for Pontiac's unfortunately.
Yeah it’s definitely heat soak, starts up fine with 18 but not reliable once hot. My band aid method was starting at 18 and retarding the timing until it started up while hot. Going to try heat wrapping the exhaust and starter with a shield and see how that gets me before I crank up the timing. Was interested in a mini starter but they can be pricey, also not what I wanted to hear in terms of install, sounds like a pain. In terms of cables, the positive coming from the battery is significantly higher gauge than the red wires. There is definitely room for improvement there. Contacts should be clean. Thanks.
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Well, for sure, the starter is honest. If you r e t ard the timing just far enough to start it, then that's perfectly a fine place to be, no matter what the timing marks say. That's good info to have. If the starter is dragging rather than "kicking back" then it may be accurate.
I enjoy trying to troubleshooot carburetors, but not so much via internet. I don't have much to add here.
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Well, for sure, the starter is honest. If you r e t ard the timing just far enough to start it, then that's perfectly a fine place to be, no matter what the timing marks say. That's good info to have. If the starter is dragging rather than "kicking back" then it may be accurate.
I enjoy trying to troubleshooot carburetors, but not so much via internet. I don't have much to add here.
Appreciate the input, internet isn’t a great medium unless it’s videos in terms of carb troubleshooting but any info is good info. Not sure the definition of kick back vs dragging, starter sounds like any heat soak starter does or a dead battery, it will keep spinning the engine but not fast enough for anything to boom, normally getting pushed back by compression when I let off.
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Have you verified your timing marks on your balancer to make sure it hasn’t spun or you haven’t jumped a tooth?
Small side note, when I had header relate hot start issues I found that wrapping the header and leaving the starter unwrapped gave me the best result. Wrapping the starter itself allowed it to heat and seemed to prevent cooling. I’ve always meant to wrap my header but my “temporary” wrap consisting of a starter wrap around the header has provided me with 8-10 years of trouble free starting with the factory starter.
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Have you verified your timing marks on your balancer to make sure it hasn’t spun or you haven’t jumped a tooth?
Small side note, when I had header relate hot start issues I found that wrapping the header and leaving the starter unwrapped gave me the best result. Wrapping the starter itself allowed it to heat and seemed to prevent cooling. I’ve always meant to wrap my header but my “temporary” wrap consisting of a starter wrap around the header has provided me with 8-10 years of trouble free starting with the factory starter.
Yeah verified timing within a degree and my harmonic seems accurate. Installed a mini starter and it is going great so far, was likely heat soak. Took it for a 30 min 80 degree drive and it started within a second after parking for a minute. Appreciate the help.
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What do you mean by “seems accurate”?
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What do you mean by “seems accurate”?
Brought piston close to tdc didn’t account for dwell or anything and the grove on the harmonic was lined up to 0ish on the timing marker. Figured it would be way off more than a degree if it were to have slipped.
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Yea I would say so too. Just wanted to double check how you verified it but sounds like you have it covered. I may have asked before but where are you located again?
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Yea I would say so too. Just wanted to double check how you verified it but sounds like you have it covered. I may have asked before but where are you located again?
Up in Minnesota, weather is finally nice enough to take the cars out. Got almost a foot of snow a few days ago now it’s in the 70s, pretty early spring for us.
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I'll say this much about troubleshooting the basic problem. I am not someone who would realistically believe the engine would run fast with the choke open due to a vacuum leak. There are two ways the throttle can stick open, the idle screw and the fast idle cam. It seems like in your case the carb simply doesn't close correctly. I haven't run into that in a rochester carb myself.