OneSunkCivic

ok here is how it is when the car is moving it is awsome but when it is idling if I tap the gas the idle jumps up for a second then once it sits there for a couple seconds it drops down real low and stays low. I was wondering if anyone has had this happen to them before? I think possible causes would be the throttle position sensor or the intake air control valve just wondering if anyone has had this problem and what they did to fix it. Thanks