check the throttle body and clean it if needed. dirt and gum build up will do that, especially if it partially blocks the inlet for the iac valve. a can of carb and choke cleaner will work. clean it up and see how it is. as a note, it will misfire and smoke a bit after intially cleaning it. drive it and see how it is

 

Ditto on what micro says. Be ready for the car to stall out several times when you are cleaning down the throttle body and associated parts. Dont let it scare you. Im betting you problem is fairly simple. If a thorough throttle cleaning doesnt help, then look for a vac leak. There are several ways to do this...

1) spray some carb cleaner around known offending areas (throttle body base, vac ports, intake manifold to head area, etc. What you are waiting to hear is any change in engine RPM.....

2) Try same procedure above, but with starting fluid. Starting fluid works MUCH better for this test but is HIGHLY volatile and is the EASIEST way to catch your car on fire. Dont laugh......you have been warned!

 

Thanks for the advice guys. I will try that out when the weather gets better here.