[richtazz]

Could be a tune-up issue, but I'd look at the IAC valve. Its a small stepper motor on the throttle body that regulates air entering the motor at idle or part throttle. It adjusts incoming air supply in accordance with engine load, and sounds like where your problem lies. You can take it off and clean it, as it is common to get gummed up by fuel deposits. Just be careful not to move the pintle too much while cleaning it, or you can mess up it's calibration. While you have it out, spray some cleaner up in the bore in the throttle body where the IAC rides, as it gets gummy too.