Engine revs up/down on its own

[fax0815]

Also worth checking the air bypass valve unter the throttlebody, they normally cause the >2000rpm idle when stuck open.

Take the Airfilter rubberpipe off the throttle body, you´ll se a few holes drilled in front of the butterfly. The big one on the side, that is the crankcase vent, there are a few smaller ones , shut then carefully with your finger, one of them is the bypass (2nd biggest hole iirc). If your engine is at operating temp and you close that hole and the idle drops low, down to 700 or less its stuck open and you need to change it...

Its a thermostatic airbypass, and just like the normal thermostat the fail sometimes.