idle air control valve, it could be dirty and you should clean it out with carb cleaner or brake cleaner. it is located on the back of your intake manifold and it should have 2 coolant lines running to it and 2 12mm bolts holding it to the intake manifold. pinch the lines and disconnect them and take the IACV off and spray the shit out of it. that should cure the problem unless you need a FITV(fast idle thermo valve) which is located on the throttle body.