Honda Gurus - 1992 Accord Idle Problems

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Axe Man

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So the kid, against my advice, brought home a 1992 Accord 2 dr coupe with a rough 150K miles. 2.2 engine, AT. Runs OK except it has a high and uncontrolled idle. Sometimes revs to 3K RPM on cold start. Eventually goes down to about 1.8K RPM engine fully hot. Never any lower when in Park. Obviously at that speed it slams into gear.

Started looking it over. First thing I noticed is that the check engine bulb is burnt out. Very suspicious. Tried cleaning the IAC, thinking that it might be dirty and stuck. Yes, it was dirty but cleaning had little effect. Idle did come down slightly. So we tried a new IAC. No difference. I did check the throttle body and the pedal linkage and it is fully closed against the stop.

Looking for some advice. Could a vacuum leak cause the idle to go high? Or perhaps a bad TPS? I don't want to just throw parts at it. For some reason the ECU is keeping the idle way up there and I'm stumped.
 
What happens if you unplug the IAC? A vacuum leak sure could cause a high idle. Unplugging the IAC usually causes it close completely, which should stall the engine out if there's no vacuum leak.

I believe these have an idle tracking switch in the TPS, too, which should close when the throttle is closed.
 
Hi Axe Man:

I had a '90 Accord with a 2.2 - same engine as the '92. One time I tried to raise the curb idle speed a bit and the PCM didn't like that a bit. It caused a surging runaway idle so I put the adjusting screw back where it originally was. It was fine again after that.

I'll bet someone messed with that screw. If memory serves (haven't had it since '99) it is a screw on the front of the throttle body that controls the amount of air bypassing the throttle plate for the baseline idle setting. It doesn't move the throttle plate at all - just controls the amount of air bypassing it. I think it had a dab of yellow paint on it from the factory.

This is what I would try: Get a short piece of wire or a paper clip. Look under the passenger side of the dash and you will see a female two-prong connector. Jump the connector with the wire and start the engine. Let it warm up completely. See how it idles now; this puts the PCM in the mode where you can adjust the baseline idle and the base ignition timing. The emissions sticker under the hood should say what the base idle should be. I think it was 650 RPM or so. If you are able to adjust it to that speed, then shut the car off and remove the jumper. Restart the engine and see how it is. The PCM will take over and hopefully you will be back in business.

If that doesn't do it, I'd bet on vacuum leaks and would also check the timing.

I hope I got it right - it has been awhile!

Andrew S.
 
Originally Posted By: brianl703
What happens if you unplug the IAC? A vacuum leak sure could cause a high idle. Unplugging the IAC usually causes it close completely, which should stall the engine out if there's no vacuum leak.

I believe these have an idle tracking switch in the TPS, too, which should close when the throttle is closed.


If I unplug the IAC the idle goes down slightly. Still not to spec and doesn't stall.

Well, seems the consensus is a vacuum leak. Guess I'll start pinching off vacuum lines and see what happens. And yes, there a MILES of vacuum lines on this engine.
 
Doesn't the distributor control the idle on those cars? Also, does that have a FITV? Those are two things I would check. You already checked the IACV so you're one step ahead of me in that aspect. Great cars if taken care of properly.
 
Not a guru on Honda but I seem to remember at thermostatically controlled bypass in the throttle body that was common to fail. Only repair was throttle body replacement.

Definitely check for vacuum leaks first though!
 
There are small coolant pipes going to the IAC,these can block or get air locks and resulting high idle.Also check the PCV valve,very prone to failure in Honda's,and giving idle problems.
 
I had to replace PCV grommets (lacked snug fit), a PCV hose (cracked), & PCV breather box o-ring(leaking)to get rid of a roaming idle on a 92 Civic.
 
Some more updates...

I pinched off every vacuum line I could find while the engine was running. Both ported vacuum lines at the throttle body as well as any lines directly to the intake manifold. No affect on the idle. It remained high. See pix...

IMG_0136.jpg


I also tried unplugging the lines while engine was running. Some caused the idle to increase however removing that one just above the throttle bellcrank (short one to the left) caused the idle to go to normal. Thinking I was on the right track I tried plugging the line and while the engine idles fine it will not accelerate while in gear. It bogs down.

With some parts diagrams on a Honda parts website I traced it back to a "Control Box" mounted on the firewall. In this box is the MAP sensor as well as some purge valves. Tracing this line and it apparently goes to the MAP. See pix of Control Box...

IMG_0137.jpg


I'm not sure why removing ported vacuum to the MAP would cause the idle to go to normal. But the engine certainly won't accelerate without it. So I'm back to square one. Any ideas would be appreciated. The MAP is just too expensive to change out and I'm certainly not convinced it's bad.
 
my frind had that car and had 200k miles on it and it still ran pretty good aside from his fuel pump dieing on him.
he had the same problem. But he didnt care.
 
Originally Posted By: dnastrau
Hi Axe Man:

I had a '90 Accord with a 2.2 - same engine as the '92. One time I tried to raise the curb idle speed a bit and the PCM didn't like that a bit. It caused a surging runaway idle so I put the adjusting screw back where it originally was. It was fine again after that.

I'll bet someone messed with that screw. If memory serves (haven't had it since '99) it is a screw on the front of the throttle body that controls the amount of air bypassing the throttle plate for the baseline idle setting. It doesn't move the throttle plate at all - just controls the amount of air bypassing it. I think it had a dab of yellow paint on it from the factory.


Andrew, are you referring to this?

IMG_0138.jpg


I didn't mess with it and I don't see any other adjustment on the throttle body.

I also can't find that connector you mentioned. Under the passenger side of the dash?
 
Bear with me, it's been a long time since I diagnosed and replaced the part for this problem. The same engines were in the old Acura Integras and we used to see this time to time. Most of those cars are gone now, so I haven't done this in a long time, however:

Most likely a bad fast idle control valve. It's a part the controls the engine high idle on startup. It's tied into the coolant system, and once the engine warms up a bit it ramps the idle down. That would be my best guess.
 
Andrew and AcuraTech are on target.

If, as Andrew suggested, the base adjustment screw was messed with, it could be causing you all sorts of problems.

Essentially the idle is completely controlled by the ECU ... so if the 'butterfly' is at all opened by that screw, I'd fix that first.

My bet would be that upon doing this, your car will not idle and die ... which would be the reason why this was messed with in the first place.

It is at this point I would follow AcuraTech in that he mentioned the fast idle control valve.

I've seen many 'older' unknowledgeable mechanics resort to this even on newer domestics. My uncle had my mom's suburban at about 1500 RPMs... for no reason other than that 'it seemed like it wanted to quit'. New IAC fixed the problem. Had to back down the throttle he should have not jacked with.
 
Good point by HondaMan. If you jack around with the idle screw without doing the correct procedure, the idle is gonna be goofy.

The idle screw should be on the throttle body, above the butterfly. It's a flathead screw that is slightly recessed from the throttle body itself. You can tell if someone has been jacking around with it just by looking and seeing if the screw head is halfway stripped out.

It's not like a carburetor where you can just turn the screw, there's a specific procedure, can't remember it off hand.
 
Last edited:
Guys, thanks for the input. I found the idle screw by looking at the parts diagram. When I get a chance I'll check it.

I also found that fast idle valve. If the idle screw on throttle body is properly set and it still idles high is there anyway to isolate the fast idle valve? For example, if the engine is at operating temp can I remove the valve and plug the port in the manifold and see if the engine idles lower? Like I said I just don't want to throw parts at it without proper diagnosis.
 
Originally Posted By: AcuraTech
Good point by HondaMan. If you jack around with the idle screw without doing the correct procedure, the idle is gonna be goofy.

The idle screw should be on the throttle body, above the butterfly. It's a flathead screw that is slightly recessed from the throttle body itself. You can tell if someone has been jacking around with it just by looking and seeing if the screw head is halfway stripped out.

It's not like a carburetor where you can just turn the screw, there's a specific procedure, can't remember it off hand.


I had similar problem with my 91 Accord SE with F22A6 engine. Yes, there is a specific procedure to adjust that idle screw (per Honda FSM) but I adjusted that screw 1/2 circle - clockwise, one at a time and it fixed high idle problem.

Another problematic area @150k is oil filter housing gasket. It was very common to this car / engine. My failed and I was home with less than 1/2 qt of oil. Got my at 125k, sold at 145k.
 
You need to check if the coolant is circulating at the idle control valve - if it's not seeing operating temp,it will go to cold start idle speed,hence the high idle.
 
You absolutely can cover the idle speed port; I have not done it on a honda but generally you take the air intake tube off and cover it with your thumb! You have a MAP sensor so you don't have any MAF sensor to worry about having airflow over so you can run it without the intake tubes attached.

This thermostatic bypass is a gimmick to warm up the catalytic convertor within 90 seconds or whatever the EPA says. The computer controlled idle speed controller should have enough travel to give more air when the car and the oil is cold for an acceptable idle. Odd to see both devices installed (more parts); usually the computerized ISC is all you get and it handles the cold start idle.

If you have a mity-vac stick it on the line from the TB to the MAP sensor and pump away. Should hold a vacuum. Should also be a way to splice a voltmeter into the MAP sensor and see it move with the key on, engine off. Shoot you could plug the TB port and mityvac (or suck through your mouth like a straw) the MAP vacuum line with the car idling. See if you change the tone of the idle or get it to blow black smoke. Any effect indicates the system is semi-working. May just be leaky in that hose.

So the kid brought home a basket case, but if he/you get it running right he can surely sell it at a profit, people love hondas!
 
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