1997 Camaro Z28 LT1 A4 112k miles. Stock

I have a weird Idle problem. After I have been driving my car for a while when it warms up, my rpms keep climbing when I'm driving, so even when I have my foot off the peddle I keep going faster. When I come to a stop my idle is around 1500 RPMS, so I have to give it a little gas before it will drop back down to a normal idle. I have recently put new Plugs, wires, O2 sensors, pcv valve, fuel filter, Induction Flush etc... I have no Check Engine light on which leads me to believe it could possibly be a bad throttle cable, or is possibly sticking... however it only does it after I have been driving it for a while. I originally thought it was from my intake manifold leaking but I had that fixed as well.... Could my IAC be bad? I don't have any codes being thrown though.

Any input is appreciated

Thanks

Tom

 

Sounds like it could be a vacuum/air leak. Checking your IAC is a good idea. Check for cracks in the intake elbow, or any other rubber or plastic pieces or hoses.

 

how can I check the IAC out to see if it is bad? Also, I've replaced ever single hose when I did the intake manifold. Why would it only surge when it warms up though... If I had a vacuum leak wouldn't it be surging constantly?

Tom

 

http://shbox.com/1/iac2.jpg

http://shbox.com/1/4th_gen_tech2.html#iac_reset

 

I did the Idle Relearn procedure and still have the problem.... I'm now leaning towards a vacuum leak, but don't know where to start looking. Could my throttle cable be sticking? Is there any known problems with the throttle cables on LT1's?

Tom

 

Don't rule out the IAC until you do the ohm readings.

Vacuum leaks are tricky to find. I have heard of spraying WD40 all around where the intake seals and along the hoses. If some gets into a leak that you can't see, the idle will go up slightly.