I have a 92 Civic DX that revs up and down from 1000 to 3000rpms constantly. I purchased the car not running and replaced the ecu and it fired up but #2 cyl. had low compression. The car was also revving from 1000 to 3000rpms, but i thought it might just be the computer trying to compensate for the dead cyl. I replaced the engine with the same style D15B7 and had to transfer the throttle body, dist, and every sensor the engine had. I also installed a new timing belt, water pump and thermostat. The new engine runs but still has the idle problem. The engine light is not on. I have cleaned the tb, iac, what I think is called the fit on the bottom of the tb and read every forum pertaining to my problem but have yet to find a solution. I cannot get the ignition timing set perfect because of the irratic idle. Any suggestions would be much appreciated as I am not familiar with Hondas and this one definetely has me stumped. Thanks.

Have you checked that all your vacuum lines are attached?

Yes. I can take my intake off before the throttle body and plug the hole in the tb with my finger and the engine will die so I dont believe it is a vacuum leak. I can also control the idle that way to and the surging will stop.