ok ive been messing w/ this idle problem for a while. when i start the car/ push in the clutch/ neutral, the rpms jump up to 2000 or so, then it slowly falls to normal idle speed. ive checked every vacuum hose, ok. i replaced the IAC valve, MAT sensor and reset the computer. on the 88 2.8, there is no relearn for the IAC either. i checked w/ two older GM techs and checked through the Tech 1, nada. i found a code for the MAT, EGR and VSS no signal. MAT was bad, replaced, no luck. next is the EGR. would that possibly cause my rpm problem? im going to do it anyways, but was wondering if it would cause it, i dont think it would but i havent done anything w/ an EGR in a while. im thinking my only options left are replace the intake manifold gaskets and possibly the throttle body since it may have too much play in the throttle plate causing an air leak. any other ideas are more than welcome.

 

TPS & IAC? Most common idle problems. But i'm pretty sure you've already ruled out those culprits. Wish i could help =/.

 

yea IAC and TPS are ruled out.