I Have a 1997 Honda Prelude Base and my idle goes up and down by itself. Ive replaced my idle air control valve and tested all my sensors and its still doing it. It does it when its hot/cold, anytime.

 

Any Ideas? Ive searched other threads and ive replaced what they say to replace.

 

re set your ecu???

 

so what exactly is happening? are the rpms going up and dropping or is it slowly going up and going back down? if its going up and dropping fast, check your intake manifold and make sure all vac lines are on. If its slow, re-set your ecu. If this doesn't help, i don't know what it is