While driving my car yesterday, it started to act funny. I would be driving along at a certain RPM, but then when I let off the gas to slow down the RPMs stayed where they were at. For example if I was at 3500 RPM and then let off the gas it would just stay at 3500, it was like cruise control was on. I discovered if I kind of "snapped" the throttle really fast that the RPMs would come down. Also in park it would idle around 2500, but if I snapped the gas a little it would finally come down. Any ideas? I thought maybe the IAC or TPS, but I am not sure how to test them. Also it seems a little harder to start. Thanks for any help.

 

Kind of dependson a few things as to what it might be.

Have you adjusted your TPS recently? Has it been hit while you were working under the hood? Has it just come loose? Has it gotten wet from hosing down the engine?

If it is none of the previous...
Are you running your original TB? If so, for how long? Carbon can build up and form a ridge which will make the throttle blades stick.

If it's a rebore like a 52mm TB from TPIS, resin may be leaking into the bore. When they bore the 48 larger there is a passage they have to fill with resin. This can cause the same effect as the carbon build up. Of course the 52 is supceptible to the same carbon build up that the stock TB is, also. Rebores may have the throttle blades binding in the bores. This can cause a sticking throttle.

It has been my experience that when the IAC is gummed up or having problems the car is more prone to stalling than high idle. The only time I've seen a high idle caused by the IAC was when it was disconnected.

Lastly check that your driver's side carpet isn't jammed up under the gas pedal.

 

I agree with lounge lizard. My IAC is just F'ed up. My car wanted to stall in the worst way until I unplugged it. I then turned the idle up a bit. The car ran and drives fine now. Bad IAC =stalling. High idle = sticking throttle

 

I agree. Check the IAC.

 

actually I am running an ATI Procharger and yesterday I had it dyno tuned. The car was fine when I drove it there. On the dyno, the rubber throttle body boot kept flying off when the guy let off the gas, this was due to the supercharger. It happened like twice so it probally did hit the TPS, what could it have done to it? Do I need a new one. It is a stock Throttle body, and I haven't touched the TPS or IAC. The car started acting up on my way home.

 

It probably just moved the TPS. It has two torx screws that hold it in position. You will need to readjust it.