iac or tps
 

my car is a 99 gt 5 speed- lately when getting off the highway or anytime im holding a certain speed/rpm for long period of time then take the car out of gear to slow down or whatever it revs up and stays up until i shut the car off and restart it. for example today i was goin down the highway at 2k rpm get to off ramp take it out of gear and the car just shoots up to 3k rpm and sticks, i reved it and it just stuck at the higher rpm i just reved to so i had to shut it off and restart, it just kept doing it the whole drive home and seems to be getting worse. I used to have this problem once every couple weeks but lately its more an more frequent. Im thinking its either the Throttle position sensor or the idle air control? what do you guys think

Go out and get it to do what it's doing and unplug one of them and note the diffrence.
To me it sounds like a TPS. I've had the same problem with other cars and turned out to be the TPS.

yea im thinking its the tps as well but the reason i also have afeeling it could be the iac is because its like somthing is getting stuck open which makes the car want to just stay reved up with extra air and fuel, im thinking the valve on the iac might be stuck? anybody else got an idea

tps more than likely. when an iac motor goes bad it shuts of the motor.

Sounds like the tps. I had my IAC screwing up and it would do the opposite, drop to real low rpm's and sometimes stall the car out.

Scott

sounds like an IAC problem, thrttl cable sticking (which there was a TSB about the thrttle cable hanging-up at the carpet) or a vac leak........just an FYI: the TPS's used on the Modular cars since 1994 has been one of THE Most Trouble-Free TPS's ever used by FoMoCo, so I doubt your problem lies wth it....stock thrttlbdy or aftermarket?

hmm this seems to happen to my car pretty often when coming to stop or putting car in neutral....I thought it was a tune problem....

vacuum leak is also a possibility... listen for whistling sounds.

i originally thought it was a vaccumn leak but i figured a vaccumn leak would create a consistant problem rather than just once in a while maybe.

can somone get me the link to the TSB on the throttle cable deal or just let me know how to fix it (do you just somhow lube the cable?) and were talking about the cable that runs from the gas pedal to the throttle body not the springs on the throttle body right?

I cleaned the IAC today, if that seems to help i think i will just get a new IAC rather than have to clean this one every couple months or whatever.

I took mine off and cleaned it with some Throttle Body/Carb cleaner and it has worked like a charm ever since! You might want to try cleaning the MAF as well, the MAF and IAC get carbon build up and especially oil if you're running a K&N filter.

Scott

try pushing on the connection on the tps and if that dosent do what your say bout that reving up n shit then try cleaning your throttle body and check where the cable come through the fire wall and mabey put a little dab of grease there