I drive a '91 Civic CX (has the D15B1 DPFI). The headgasket sprung a leak and was burning coolant (was very old, possibly still right off the factory), so I took the head off (did timing belt as well) and replaced it. Also did the O2 sensor as the old one was VERY old, plus I had broken the cable right off the sensor itself by accident. It had *zero* running problems beside burning coolant before I did the headgasket job. I of course drained the coolant to do all of this.

I've got it put back together again and, while it sounds OK, the idle spends about a second at 2-2.5k, then cuts off as if to die, then jumps back up to 2-2.5k... this cycle repeats over and over, with small variances in how long it spends at high-RPM. The coolant hoses get hot, as does the rad. Starts up just as it did before, no CEL, no codes on the ECU. The other change is the temperature gauge.. even after 15min, it doesn't pass the cold mark. The heater blows hot air and I know the coolant's circulating. What should I be looking at? From what I've read, IACV and FITV are possible culprits, but I just don't see them conveniently failing at the same exact time as a headgasket swap.

Engine has ~180K KM.

Thanks!

 

you have a problem with you iacv and your fast idle

 

ur temp sensor is bad or unpluged.so the ecu dosent know how to run making it idle funny...fix ur temp sensor

 

Sending unit for the cluster gauge was indeed unplugged (stupid me), works now and coolant temp is normal. The ECU temp sending unit (also under the distributor but bigger plug) works (or at least registers with the ECU), as the revs increase a fair bit and the engine "breathes" a lot faster if I unplug it (plus it triggers the CEL). Not too sure where to go from here - to pull that sensor for cleaning I'd have to drain the system again correct?

 

Cleaned the IACV, was fairly dirty, didn't improve anything. FITV next. If that doesn't work, I guess I'll have to pull out the multimeter and look at that ECT sensor.. just in case I can't find the right values, does anyone know what they'd have to be at normal coolant temp?

EDIT: Apparently DPFIs don't have a FITV. I don't think I've got a vaccuum leak, covering up the intake port kills the engine immediately, and I don't see any loose hoses. I'm completely stumped =(
The beginning of this video (so before his car revs to 3k) is very close to how it behaves right now: http://www.youtube.com/watch?v=DuNbP6IM6Gw

 

At normal coolant temp, the TW/ECT sensor (I think they're just alternate names for the same thing - it's the ECU's coolant temp sensor) reads about 350ohm, well within the 200-400ohm range stated in the 92-95 manual. I think this pretty much rules it out. Still stumped for what it could be, and I'm running out of ideas.

 

Got it. Freakin' sticky throttle cable. After pushing the throttle in with a screwdriver or sticking my foot *underneath* the pedal after accelerating, idle's back where it used to be, and stable. The cable still sticks, but I know what the problem is now and I can get to fixin'.

 

I have a similar problems on my wifes hatch, changed every hose, iacv, intake gasket, completely removed and cleaned the throttle body and put in a new gasket and o ring. As a result the car runs and feels allot tighter but there's still the erratic idle, going to check the throttle cable next. It had completely skipped my mind, thanks.

 

Seems like a vacuum leak to me and the iacv is trying to compensate for it. Spray brake cleaner at the tbody gasket, intake manifold gasket, even where the iacv mounts.

 

As a note, I think I had the throttle cable issue due to basically shoving the entire intake as far back as I could when I pulled the head (didn't feel like disconnecting everything), I think it messed with the cable's alignment - what I did to fix it was spraying some WD40 onto the rocking assembly on the throttlebody that the cable controls, as well as giving it more slack by giving the two adjustment nuts on the bracket just in front of that assembly a few turns.

It doesn't explain why it'd rev, cut out, and rev again over and over; if anything, it should've just maintained a higher RPM - but what matters is it works now (and very well at that, for a B1).

 

when the car is idling above 1200rpms it forces the injectors to shut of and that causes the erratic idle

 

I have a honda CRV 99, and i have a similiar problem. My temperature gauge reads cold but only when my heater is on, when i shut off my heater the temp gauge goes back to normal, in the middle. Any suggestions or does anyone know what the problem might be.

 

happened to me...spent 50bucks on an IACV...just about to recommend that.

noob bumping old posts...