Atleast from a couple of opinions from people that have the experience with the IAC on the TPI motors. Okay im fixing to buy a 91 Trans Am with only 69K original miles on it, and its pretty much perfect, and a clean motor, but the only thing is when you come to a stop light or just waiting for a long time the idle starts bounce around and go up and down shutter a little. But if u just put it in neutral at every light it idles absolutely perfect.

If you just come to a stop light and you arent really sitting there very long it idles fine in drive but after you wait a little longer then it starts bouncing around. The guy said its only died on him once but it automatically cranked right back up. So im not sure...... do yall thing its the idle air sensor?????

He had the tps and everything else around the throttle body tested, also the map sensor, and everything and the only thing he can think of that it is the IAC is gone bad. No vacuum leaks either.

 

The ECM needs to know what gear the trans is in in order to compensate for the added load the trans applies to the engine when you shift from park or neutral to drive or reverse. It needs a signal from the park-neutral switch to tell when to increase the idle speed to compensate for the added load. Im not familiar with Firebirds but usually the P/N switch is adjustable.

 

i dont follow. Are you sure? Because im just thinking its the sensor. Because it idles fine accept when ur waiting at a light in drive for a while it seems to just want to bounce. other than that the car is fine, and the transmission was just rebuilt on it 1500 miles ago.

 

I can't say for sure what the problem is without getting my hands on the car and performing some basic checks. Im just giving you some possibilities to check. It very well could be the IAC but whatever you do don't replace anything until your sure you've isolated the problem.

I did a quick search and found a post with a similiar problem. Turned out to be a bad inj.

https://www.thirdgen.org/forums/tpi/...ght=stalls+out