Sometimes my car will randomly decide that it needs to idle at anywhere from 2500-3800 RPM. If you blip the throttle all the way open, the rpm's spike, drop to normal then go back to where they were. I.E. 3500 to 4500 to 1400 back to 3600. I've messed with the throttle linkage, and that's fine. The butterfly closes all the way, but the idle is unreal.