Hi all. Got a 92 honda civic dx. I'm not sure what exactly's going on, but for some reason the car's been idling high when the engine temp's at the halfway point. It's been sporadic though, because there've been a couple times the car's idled normally at .7k rpm's, but then for no reason it'll keep reving in neutral. I have a weird feeling it could be an O2 sensor going crazy. Any ideas? Thanks.

-Jon

 

do the revs go up and down by themselves at idle, kind of like at a pulse?
and the idle is high even when it's in the trough of the surge?

i don't see any way an o2 sensor would be linked to this.

my first ideas are IACV and FITV (idle air control valve, fast idle valve)

 

I agree. Try cleaning the IACV (EACV) and FITV. Greddy_Civic's DIY method for cleaning the IACV should help with both.

Both valves are located on the throttle body and there is a relatively simple test for FITV malfunction:

 

Well first, trustdestruction, the symptoms are that it surges once in a while, but, for instance, one day it'll be higher, say 1200rpms, another day 900-1000, another 1500. This usually seems to happen especially after I drive for a while, also. Kind of weird.

And yeah, I did that test, seeing if there's suction after the engine's warmed up, and basically there was--strong suction. The engine was idling maybe about 900-1000 rpms at the time. That picture said to replace the valve, seeing that I guess it's leaking...how would I do that, and how much are those usually? Thanks!

 

i actually just replaced mine for surging idle (the wax piece went bad and was leaking coolant into the intake manifold)

i think it was around 70 bucks brand new from Honda. Oh, and you won't find it at any auto parts store. You could get it at a junkyard I suppose, but with the wax piece being degradable, i'd just spend the extra cash for a brand new one. It comes with all seals and everything.

I bought mine from my dealer, i needed it the next day because my surging problem was a little more severe (up to 3k RPM surge).
Check hondaautomotiveparts.com, they deliver so it might be a few more days but they sell them a little cheaper, and your dealer most likely won't have it in stock anyway, they'll have to order it.

 

Before purchasing a new FITV, try cleaning it. The port through which air flows commonly becomes clogged with soot, causing it to stick open. The cleaning procedure is similar to that of the IACV port, which is described in the forum DIY section.

 

So, heh, 4 months later... I fixed it.

Gist is, well, other than 4 months of being lazy and doing nothing, I finally got around to cleaning the FITV. Weird thing was, the inside of the valve looked perfectly clean, like the clean pictures in the how-to. I still cleaned out the inside with carb cleaner. And then another weird thing, the inside of the coolant outlet, on the FITV, looked like it was semi-clogged with gunk, so I ran some water through that port to clear out the gunk. Anyway, just to make sure the FITV wasn't letting in more air than it should, in case the wax piece inside was screwed--this is what I partially suspect now--I tightened the cap back on to the valve to within a revolution or two of being completely tightened--basically so only a little air clearance is allowed. Stuck the thing back on and connected everything, Civic's worked like a charm ever since.

The only side effect at the moment, if it is a side effect, is that when I start up the car, it's a little weak on the initial idle--that is, it'd be up at maybe 1000-1200 rpm's, which might be normal, but it sounds like it could be a little higher or something. This could also just be a consequence of screwing the cap on so the fast idle doesn't really add a lot of idle to the whole thing, at least at start up. Nit-picks aside though, it's working pretty much like normal now. I think I might have to replace either the wax piece or the whole FITV eventually though, if the fast idle setting should be higher than it is now. But I'm not going to worry about that for now, doesn't seem essential so long as everything works like it should more or less. Yay!

EDIT: Forgot to mention, I think the gunk in the coolant outlet might be a consequence of either some coolant stop-leak I put in to the system last summer, or also a little oil that might be mixed with the coolant. The latter, because I took out the cylinder head to be rebuilt, last sept., and haven't quite gotten to flushing the cooling system yet. I'm about to soon though.

Random question, is it fatal if there's oil mixed in the cooling system?

 

My 2000 civic had the same problem and eventually it was an easy fix. I took a 12 mm wrench and loosened off the throttle cable. As I did this the idle went down to normal. I believe that the throttle return spring is getting old and with the heat of the engine it is expanding causing the engine to race at high RPM. I hope this helps people out.