my car for weeks was idleing at 640 like it should, which is perfect and i like it. then all of a sudden sometimes i would start the car and leave for 20 minutes, come back it would be idling at 1400. id shut the car off, turn it back on and the idle would be 640 again.

does that sometimes now. also i was sitting at a light with a car in front of me, and it was idleing at 640, the rpms shot up to 1000+ and the car lunged forward. sort of scared me.

sucks when im sitting on snow with the brakes light pressed, and the car idles high causing the tire to spin by itself.

I had that problem too digital, it is a PITA because you cannot define a position for the screw. Why do not you check this, disconnect the IAC connector when the car reaches operating temp. After that, shut it off, start it again, and see how it is idling.....turn the air screw to regulate RPMs ( in overdrive gear). Once it idles fine, turn it off, reconnect the IAC connector and start it again....if the car idles fine, check the TPS to make sure that it is in the right position. Let's see what happens with this procedure.

Or a simple search reveals the real proceedure... https://www.thirdgen.org/techbb2/sho...t=minimum+idle

haha TechSmurf I did not have that one!! but I can tell you that the one I said is ok too. Thanks for all man!

No.. it really isn't. What we have here is a clear-cut case between the 'wrong way' to do something (the hack job that might work) and the 'right way' (GM Technical service proceedures). Which proceedures our users advise other users to use is what sets us apart from ALOT of other automotive forums out there. I'm not about to comprimise quality control.

85berlinetta2.8, have you changed your minimum idle at any point to compensate for a low idle or something? It's possible other things are wrong, like your PCV system being clogged up and working intermittently (this would wreak havoc on idle stability), or your IAC could just be going out (when's the last time you changed it?)

ive taken the iac out and cleaned it, almost all the parts on my car are original except the pcv, wires, plugs, tps, and air filters i think.

when the car revs high i can unplug the iac and plug it back in and the cars idle will return to normal.

Pull your PCV valve out with the car running and make sure there's good vacuum at the bottom of the valve (It should be restricted by the valve itself, but the vaccum should be quite noticable.)

https://www.thirdgen.org/techbb2/sho...hreadid=275841
check out this because it give different techniques on how to help this problem.