sometimes when i start my car, my car will idle at like 2000 rpm! but here's the thing....if i wait a long while, it sharply drops down to where it should be. sometimes it doesn't drop down, so I'll go drive and while i'm driving, my rpms will be about a whole 1000 rpm higher than it should be, but sometimes it will drop down to normal again. what's wrong, is there an electrical problem, or do i have something in my pipes?? help me out, because it's really annoying, and I'm not sure if I'm wasting more gas than I should be. this has been going on for like 3 months.