When I start the car up, it goes up to about 2000rpms and then it almost wants to die, idleing around 500rpms. Then after about 2 seconds it goes back up to 2000rpms and stays there. While driving, totally warmed up, the car has no consistant idle. Sometimes it idles at 2000rpms, sometimes it idles at 1000rpms, never lower. There is no fluctuation though. Any Ideas?