Ever since I had my car, which is a 1987 Pontiac Trans Am, it would idle strange. Like for instance I'll be on the highway and when i take a ramp to a stop or slow down my idle stays up near 1800 or so. At first I thought the throttle body for the tpi was sticking but if i wait about 15 to 30 seconds it will come down on its own. I have checked everything i can think of I ever replaced the IAC valve and it still does it. At first it was a 305tpi with a 5 speed and now it is a 350tpi with a 6 speed and factory 350tpi chip. It has done it no matter what.

 

Have same problem if u find the fix let me know plz

 

I have the EXACT problem, but its only occasional and normally does it if I accidently stall it out or it dies and I start it right back up after it dies. What I have guessed it to be are the injectors or timing...since I currently know those are my two problems with the car at this time (just haven't got around to fixing it yet.) I believe the TPS can cause this issue, but normally if your TPS was off at all, your check engine light would be on. Is it doing anything else abnormal? Ohm all your injectors after the car is good and hot with the engine shut off. Unplug them one at a time as you check each one. I think they are supposed to ohm around 16 i think, I may be wrong lol. I couldn't tell ya since mine are so whacked up. I got mine going anywhere between 11 and 16, while one is stuck around 3-4 ohms which is a BAD injector...could be causing the others to be off somewhat i assume. I hope to get these fixed this week, I'll let you know how she runs afterward. oh ya...I did notice it do the idle issue a lot less after I had my cat checked and replaced the exhaust pipe running from the cat (had lots of tiny holes in it) I know its a lot to check but I think it has to be something in one or more of these areas. Hope this helps, lemme know if it does.

 

i have a similar problem but idk what the iac valve could use some help there so i can check it

 

Make sure that the IAC valve is gapped correctly. If you got a Haynes manual it'll tell you how its supposed to be gapped...I'm not sure if gapped is the correct way of saying what I'm talking about but close enough lol

 

Oh, and check the MAF.... it could be the problem since that is a common issue with the TPIs and i believe thats the symptom for it...couldn't remember when mine had stopped doing that problem like yours until now, and it was the MAF, which I had replaced a few months back. The best way to test it is to unplug it (when the engine off) and crank her and take her for a drive then see if acts the same. If it acts the same with very lil or no change, then its MOST LIKELY the MAF. If its not the MAF, it would probably run even worse than before so you would be adding to the problem meaning that it can't be the MAF thats the problem in the first place. lol i'm sure you get what I mean. Give it a try and lemme know how it goes....