First of all, is your "Check engine" light illuminated? If so, have it hooked to a scanner. If your crankshaft or camshaft sensors are faulty, then they should set a code (But not always)
If not, then the first thing I'd look for is a vacuum leak. Look at the hoses near the PCV valve, the brake booster, EGR valve, and the MAP sensor if your engine uses one.
If there's no leak, and no trouble codes, check the throttle cable/plate for sticking.
Then the last place to check is the IAC valve and the electronic/vacuum lines that are hooked to it.
Thursday, December 31st, 2009 AT 1:56 PM