Archive for 1987 to 1991 Honda Civic Sedan Owners Club
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Idle Issues

So here is the problem I am having:
When the engine is cold the Idle spikes up to 3k, then wavers its way down to around 750, this usually lasts about 5 minutes. After this process it is usually good to go. But sometimes (not all the time) when I push in the clutch to stop at a stop sign, it will start fluctuating again between 750 and 1500.
When it is really cold in the morning (around 20 degrees F) the engine stalls numerous times before starting, then sometimes throws a IACV code (14 blinks), causing me to reset the ECU and try again until the above (first paragraph) happens.

The ECU is not throwing any trouble codes.

I have a 3rd Generation DOHC ZC run by a PM7 ECU.

I have replaced the following Items:
IACV (EACV) and Seal - replaced with parts for a 91 Civic Si
Intake Air Temperature Sensor and Seal - replaced with parts for a 91 Civic Si
PCV Valve and Tubing to Breather Chamber- replaced with parts for a 91 Civic Si
Intake Manifold Gasket - replaced with part for a 89 Integra RS
Throttle Body Gasket - replaced with part for a 91 Civic Si
Fuel Pressure Regulator and Seal - replaced with part for a 99 Civic Si
Oxygen Sensor - replaced with part for a 91 Civic LX
Throttle Cable - replaced with part for a 91 CRX Si
New O-rings and Seal around the Fuel Injectors - replaced with parts for a 91 Civic Si
Replaced all Vacuum Hoses with new ones

*All parts above were purchased brand new from Honda, minus the vacuum hoses*

In addition, I have done the following things:
adjusted/checked the Throttle Position Sensor
completely cleaned out the Intake Manifold and Throttle Body
adjusted the Throttle Cable
adjusted the Idle Control Screw
Bled the Cooling System

I am running out of Ideas.
I am currently thinking that the wiring for the IACV plug is faulty and this is causing intermittent issues ( I did not perform the swap and have a little confidence in those who did, that is the last time I pay some one else to do...anyway).
I am curious if anyone else has any ideas.

check your wiring on your IACV plug.
if thats the only code it ever throws, and its not idling correctly, i'd guess as you have that the wiring to it is faulty.

good luck Very Happy

you should have something that looks like this either under your throttle body, like this one, or on the side of your intake mani. somewhere

take it apart and clean it, and when you reassemble it screw the white plug all the way down

I think its ur fast idle as shown above, my fast idle control broke a couple times becarefull when u open it sometimes springs and small piece fall out, just take one off any civic integra except the d15 2injector, brand new at autozone cost $180. I got tired of the thing poping out unscrewing it self I I took it out add some glue to threads and screwed it tightly. Or u can get the obd 2 gsr throttle body which doesn't have it.

My throttle body doesn't have a FITV, only a passage for coolant (which has been by-passed). I was having the problem before I by-passed the throttle body, so I'm pretty sure that isn't the problem either.
Thanks for the thoughts guys.

U might wanna check if that brass screw is loose or tight

or switch throttle body try it out!

U might wanna check if that brass screw is loose or tight

He doesn't have the FITV.

~Sp33~ wrote:
U might wanna check if that brass screw is loose or tight

He doesn't have the FITV.

i know, theres this screw thing on top of the tb

or try cleaning the IACV

The IACV is pretty much brand new, installed it about 3months ago and cleaned it out and reinstalled it a couple weeks ago when I replaced the intake manifold gasket.
So this weekend I double checked all the wiring for the engine and corrected somethings, fired it up and still had the same problem.
I also swapped the PM7 for a PM8 (I think its from a CRX HF) and the problem still continued. So I dont think it's the ECU.

So the only ideas I have now are that its either:
the MAP sensor
the wiring for the IACV is flipped (positive is hitting negative and vice versa)
or my fuel pump is going out.

I find it hard to believe I am the only person to ever have this problem or atleast to this degree, I mean my luck is usually bad, but not that bad.

I really appreciate all the ideas.

Mine used to fluctuate between 1500 - 800 and back again.

I replaced heaps of crap, it all did nothing. (new IACV, Map sensor, Vac lines, FITV). It doesn't do it anymore, though it seems to have chosen not to on it's own accord.

If only I could get  so lucky, hopefully it decides to work itself out.

its either you dont have constant coolant running to your iac. or it could be a pcv valve somewhere. either the charcoal canister or the one on the smog box behind the motor or the one between intake manifold.

I'll have to look into those PCV valves..thanks.

New Information, so I went to bleed my cooling system this morning, thinking that I may have a bubble some where. Pulled the radiator cap started the engine (like my manual says) and proceeded to let it warm up. The engine proceeded to idle at 4k until after 10 minutes of listeninig to it rev and ooze coolant from the filler neck, I decided to shut it down. I put the Radiator cap back on and started up the engine, at which point it did its usually fluctuating idle trick.

Does anyone think this could point to either a bad thermostat, bad radiator cap, or something else cooling related?

It idles at 4k!?

You must have a vacuum leak man.

it only idle'd at 4k when the rad cap was off.
Once its done with its warm-up process it usually idles around 750-1000.

4GSEDAN wrote:
it only idle'd at 4k when the rad cap was off.
Once its done with its warm-up process it usually idles around 750-1000.

That's not right at all. Removing the radiator cap shouldn't alter your idle in the slightest.

Yeah, after messing with it this weekend I think it may have just been bad timing.
Although I think I may have found the cause of my problem. I was skimming through and realized I was missing the dashpot on the side of my throttle body (which I guess you can run without, but isn't recommended for automatics or cars with A/C). I have A/C. Also, my throttle plate stop (little screw that tells the throttle plate to stop closing) is set so that the butterfly closes completely. I think this may be starving my engine of air and causing it to try and run off the EACV (IACV).

Got parts on the way, so we shall see what happens.

Interesting. Let me know how she goes.
Type-S EF

That set screw is supposed to let the throttle body close all the way, or close enough that you can just assume it is, its bad to have the plate hitting the housing, it will make a groove and then your throttle will stick when slapped shut, but that's not my point, when the throttle is closed, all air required for idle, (the slowest it will idle, or the speed it idles with the IACV unplugged) should be through the air bleed.  The brass screw on the throttle body itself.  All additional air, to compensate for load, example, alternator load, A/C, putting an auto into gear. taken care of by the IACV.

I think the dashpot you call it is a vacuum solenoid which doesn't let the throttle close all the way unless there is sufficient vacuum to pull it, its just for starting, and if yours starts easy, don't bother.

Sounds to me like your idle problem is from a bubble forming in your coolant ether because of a bad head gasket or a warped or cracked head, and your code is corrosion, wiring, or faulty IACV (not many people buy new honda IACV's and that one might have been dropped or knocked around, the insides are very sensitive to shock)

Sorry, haven't been able to reply for a while.

Yeah you're completely right about the diaphram (dashpot). I bought a new idle control screw (brass screw on the TB) and coolant temperature sensor. Niether had any effect. I also replaced the thermostat and bleed the coolant. That had no effect either.

So I decided to block off the IACV. After stalling five or six times it fired up and ran fine. So I decided to hook up my old IACV to the plug so that I could see what the plunger inside the IACV was doing. It seemed to be very twitchy where it would open, then slam shut then open; very inconsistent or smooth.

I have no clue what to do next.

I had te same problem in my second ef. I replaced the iacv and the tps along with vaccum lines and it solved the problem. But you can always junk it and go d16 or even b18:) Forum Index -> Drivetrain
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