Hello,
I bought my son a '79 Firebird and we haven't had long at all. In CA, getting the vehicle smogged is required before it can be registered. We took it to the smog station and while idle the RPM was running at 2500. I took it to a mechanic when I first bought it and he checked everything out but said nothing was wrong with it and the car was fine. Any ideas on why the car would be running so high while idle? Anything a novice person like myself could check? Thank you!
You will need to remove the air cleaner to access the following; Verify curb idle screw position it should only be screwed in a few turns it is on drivers side of carburator, high idle could be sticking as well. Check if the throttle linkage is resting on the screw too, there is a little tab on the linkage following the throttle cable that is supposed to rest on the curb idle screw. Either your throttle blades are open because of the screw, or they are stuck. You could also be dealing with vacuum leaks which is more likely. Once you verified throttle position, Check all vacuum lines verify nothing is unhooked or cracked. You can also place your hand above the primaries, it is where the choke flap is ontop of the carb, if you close that area and the idle is unchanged or picks up there is a leak somewhere. if you don't see anything use propane (safer) or spray carb cleaner around the intake, carb, etc If idle picks up when sprayed then there is a leak around that area. Careful when the engine is hot.
A 79 T/A should idle under 800, I think high idle is normally around 1800, 2500 is screaming high.
If you would like video assistance, there are videos all over YouTube explaining high idle or vacuum leaks, won't find anything specific to the trans am but the causes are normally the same.
