97 Malibu with surging idle

[fritcr]

It has the 3.1 v6 and when I first start it esp the idle surges up and down. It will settle down some after a few minutes but will from time to time in gear or not still surge a bit at idle. The car runs perfect down the road. I can't find a vaccum leak. I don't know what else it could be. I have replaced the PCV valve.
Rob

[maxwedge]

Any check engine lites? Lots of possibilities here.

[steve_o]

Might take a look at the Idle Air Control Valve (AIC). Mine was gunked up with black soot and was causing a strange surge.

The idle control valve is a solenoid operated valve that lets air by-pass the closed (at idle) throttle plate, thus allowing the car to idle. Idle speed is adjusted by the computer by opening and closing the valve. After making sure the device had power and was not shorted, I removed the valve from the manifold and discovered that the valve could hardly move because of all the gummy black stuff on it. If I remember correctly, I removed the two torx screws that attach the solenoid to the valve and sprayed the valve with intake cleaner. Using an old tooth brush and Q-Tip, I scrubbed out the gunk. Don't submerse it for it has an electrical component.

It can have many names for example idle air bypass and etc.

[fritcr]

Thanks for the tips. I do not and have never had a check light. I will see if I can find the IAC on it. I did clean the throtle plate with cleaner really good when I bought it.
ROB

[kev23]

Mine did the same thing. Was wavering up and down maybe 200 rpm, usually on a cold start. Had the IAC apart but found nothing wrong with it. Figured it was just another quirk.

[fritcr]

I cleaned the IAC and it was gummed up a bit in there with black stuff. The car does idle better now after it warms up but still kinda goes crazy for a few seconds when cold. After that it idles perfect. I'm happy. I imagine that IAC is starting to go bad but I'm not going to mess with it unless it gets worse or starts doing it at a stop light again.
Rob

Thanks for the help!