My car idles extremely high (by that, I mean the sound it makes. It races when I start it. As long as it's in park the engine races, when I shift out of park, it stops). Recently it has also started acting up when I'm taking off from being stopped. It hesitates alot as I accelerate, revs up, and finally shifts. It doesn't really jerk when it shifts, but it does hesitate quite alot and it worries me. What could it be? I've checked the transmission fluid already.