Hi, I just put a used low milage 3.0 engine in my 2000 ex accord.{new timing belt-water pump-adjusters-spark plugs-oil- anti freeze-and burped the system -it sounds great... I tried the upper plenum off both engines {the old engine broke timing belt but ran great until that happened } it has a cold start idle of 2000 rpm then when computor takes over it surges between 1200 to 1900 rpm continuisly- eventually it sets a code 0505 I checked for a vacuum leak with carb cleaner and smoke-- nouthing... Is it possible for both iac valves to be bad-- I also checked the iac by disconnecting the one on the car and hooking up the extra one{ in my hand} and I don't see anything moving inside it--does the rod move in them? It isn't very dirty inside either.. It doesn't seem to me that both iac valves could be bad-- what do you think...

Its very possible that the IAC is bad. The other could be the TPS (Throttle Position Sensor) since the RPMs are running at 1200, also check and clean your mass air flow sensor. Plus P0505 is for the IAC anyway. You can check for voltage, but if you are not seeing the rod move then that's your problem anyway.I would first start by replace the IAC then go on from there

Yea it was the iac- Now I'm getting a front oxygen sensor code... Computorized vehicles are good when their good but horrible when their bad.. Thanks