zanjero

'98 Civic DX, non-VTEC, D16Y7 motor...up/down surging every 3-4 seconds. Removed and cleaned IAC valve with throttle cleaner (it was gunked up) along with the throttle body, and the symptom persists after reinstall. Removed IAC electrical connector and noted RPM drop and surging every 1/2 seconds - very quick. Reconnected IAC connection and 3-4 second surging returned. Pulled codes P0505, P0420...2 weeks prior only P0505 was present. Symptom was present 4 weeks ago at time of purchase, but has been very driveable when not stopped and having to listen to the dang up/down surge.
Don't know how to proceed at this point other than buy a surprisingly expensive IAC valve. Any suggestions on the infamous Honda idle surge issue?

rayhaque

I had this problem on my 99 Civic after having parked it for a while. Unfortunately, I was not able to remove the valve as the two little screws rotted/rusted to crap. Eventually I am going to have to drill them out.

But in the mean time, I was able to remove the "backing plate" (?) and spray cleaner directly into the valve. It was a little nerve-racking because there is a spring in there. So when the plate popped off, a little green cap and spring popped out. And then I had to figure out the correct way to put it back together.

Also ... after spraying it THOROUGHLY with carb/throttle body cleaner (CHEM-12) it still looked dirty as hell inside with black carbon stuff. But ... after I re-assembled the problem was gone!

zanjero

Rayhaque, thanks for the insight. I suspect you have a Vtec engine cuz the IAC valve is different on mine, a non-VTEC engine. There's no real "plate" on the IAC. I just took the front part off - the part that comes off with 4 bolts and has the two nipples for the collant -- and then cleaned that part out with throttle cleaner. Didn't help. Am I missing something?