When I say vacuum leak, I mean that uncontrolled air is entering the intake somewhere. It could be the throttle plate, bad air boost valve, or a normal vacuum leak.

This kind of air leak will cause the idle to surge, because it has happened to me with my FITV. I think the IAC will try to adjust the idle and can't overcome the intake.

I'll take a closer look at my shop manual to try and give better testing advise.

Air in the cooling system can also cause this, so remove the radiator cap when the engine is cold and fill up the radiator with coolant if needed.

 

any luck with the testing procedures?

 

Completely forgot about this.

Google 62sn700.pdf and download that document.

That is a shop manual for a 93 accord that I think is non-US. It will be close to your 92 accord for most (if not all) components. The voltages at the sensors will be correct and the wire colors should be the same. Verify ECU/TCU pins definitely by wire color. There are pinouts of ECUs on the web you can use as a reference as well.

 

Just a "spit ball" idea. Is the PCV seated properly and also check the hose from the valve to the intake in good condition?

 

So its been awhile and my brother took his car back and I haven't been able to touch it until today. No progress has been made. I have tried swapping Idle control valves, fast idle valves, surge valves, in various combinations and nothing makes a difference.

One thing I did, was find a service manual with a million and a half pages of technical stuff but it all has to do with check engine light codes and testing ecu's with a spare good one. Both of those I do not have. No check engine light or codes, and no spare ecu.

I have not messed with the idle setting but with the manual I was able to reset the throttle cable to the correct position and now when I plug both holes before the throttle body valve it dies like it should. That seemed like some good news to me, however plugging either hole separately does not help or change the situation at all. Plugging one, not dependent on which one, might drop the rpms a bit, but does not stop the surging or bring it to the correct rpm level.

I checked the MAP sensor for correct voltage at idle but with the surge I couldn't get a vacuum reading and don't have a vacuum pump and I don't know what the voltages should be other than 5v starting point.

So now that the car will die when the two holes are plugged it seems to me that either the IAC or FIAC is bad or both or something is telling the IAC to not behave how it should. Now there is no electrical connection for the Fast idle valve and I have tried three different ones now including the original with no change. So to me it leaves the Idle control valve being faulty either by itself or something computer wise telling it to not behave properly.

Agree, disagree, theories, suggestions, testing procedures for anything?

No shops want anything to do with my brothers car because of the age and it being obd1. I am unable to find a reasonably priced live scan tool that I can get or use in a timely fashion and the dealerships even say they can't guarantee they can find the problem.

 

My '92 5 spd manual does this for about 45 seconds during warm-up. What do I do?
I go out and start it 5 min before I'm to take off. It's all done and drives clean then.

 

I'll cross-post this as a "PSA - Public Savings Alert": If you are going to replace the I.A.C. Valve, and opt for aftermarket (which I do all of the time with generally good results); do yourself a favor and BUY TWO...lest you get a bad one, and not know it... Having had to bear the time/expense of pulling the original {Denso}, believed bad, and swapping with a Driveworks {AdvaceAuto non-OEM}, I was thrown by exactly the same "hunting" behavior.

Ultimately, forsaking 'what are the chances of both bad?' thoughts, I swapped in the much more expensive OEM part - and PROBLEM SOLVED. Now; I suspect if I had bought a few aftermarkets, one would have worked fine. It's easy to pull and replace, so you can save money there (with not much to the innards, on a near twenty year old car, etc...) - just be aware that you can easily get a DoA part if you don't buy from the stealership.

Be advised - decide up front!