pull you iac (idle air control) valve and clean it also clean your throttle body...carb cleaner and toothbrush if that doesnt solve your problem take a small propane torch, tape off the air holes on the tip. DONT light it obviously. start your car and start tracing hoses with propane. when you come across a vacuum leak with the propane the idle will fluxuate TAKE YOUR TIME if you run across a leak too fast it wont work. good luck