Following the headgasket repair on my 1993 1.5 Civic, the fast idle is higher than normal for a 10sec or so period, and then it hunts high/low. I read all of the posts that I could find. Firstly I thought since I had just done a headgasket I must have air in the cooling system. I bled and re-bled, using the manual as a guide. No luck. Yesterday I took off the EACV (IACV) and cleaned the screen and ports using carb cleaner, no luck. This morning I still had the hunting fast idle. I have looked hard for any vacuum lines that were mis-routed and/or broken and cannot find any. I labeled everything really well before disassembly. This could all be circumstantial since the weather has just now turned cold(er) in Dallas resulting in a fast idle start, but I still think it related to my repair. Question: Anyone out there have any other ideas as to what this could be?

Thanks,

Ed Fisher
Dallas, Tx

 

Unplug the IACV it should slow down. If it does that probably means the ECU is getting bad readings from the ECT sensor and thinking the engine is cold when it is not.

Your FITV could be stuck open. To check that, remove the air intake pipe and see which of the holes in the side of the TB before the throttle plate is drawing air. The one on the bottom leads to the FITV. It should be closed off when coolant temperature is above 60 F.

 

Thanks MK. The FITV thermal wax was loose within the housing. Everything in there was already clean, as I flush coolant regularly along with the other fluids, so just a tightening was required. What was confusing is that the fail manifested itself directly after the head gasket replacement. I have learned to look at the last thing done for those problems. In this case, it may have been that the unit was somewhat loose and having the intake manifold off and in every conceivable position just loosened it more to fail. I also disconnected the IACV and verified the idle at 400, back to 700 upon reconnection. All is well again with the trusty Civic, thanks for the posting, as always it is appreciated.

Ed Fisher
Dallas, Tx