1990 GS ideling problem when warm, need help

To the expert out there:
I have a 1990 Acura Integra GS with Ideling problem. The car will warm up to normal temperature and the idel will still be around 1500 rpm. When in
Drive, it revs around 1100 rpm and when you put the car in neutral, the engine will rev up to 1500 rpm then drop to 1000 rpm then up to 1500 rpm then down to 1000 rpm. Some times I can give it more gas and rev the engine up to 2500 rpm and some times it will drop down to 800 rpm, the normal idel speed. I have a factory manual and the trouble shooting guide points at two components. The book talks about the EACV and Fast Idle Valve. The book does give up the direction on trouble shooting the problem. I figure it will not hurt to see if there are experts out there that can tell from my description and provide some pointer. Any help will be appreciated.
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Remove the big air pipe to the throttle body. Just inside the throttle body before the throttle plate, you will find two big holes. The lower one goes to the Fast Idle Valve, the upper one goes to the EACV. With the engine fully warm and idling too fast, plug each hole in turn with your finger and see if the idle drops. If so, that's the thing that's bad.
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TeGGeR®

The Unofficial Honda/Acura FAQ
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TeGGeR® wrote:

I tried what you have suggested. What I found out when I tried to loose the big air pipe is that the pipe clamp is completely loose. Apparantly, the last mechanic that did the work forgot to tighten the pipe clamp back up. I did what you have suggested and the result is that blocking the lower hole has no effect the the engine while blocking the upper hole caused the engine to die. Since the Big Air pipe was loose, could the dust got inside some of the EACV and cause it to jam? Can the EACV be dis-assembled and cleaned and put back? Can you explain to me why my engine when warm will rev. from 1000 rpm to 1500 rpm and down to 1000 rpm and back up to 1500 rpm? What is the EACV doing in layman's term.
Thank.
Peter Koo
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This is good.
If the engine was fully warm when you checked, that is.

Possible faulty EACV.
You DID do this with the engine FULLY hot, did you? Assuming you did...
Now do one more very important test: Unplug the EACV's electrical connector. Does the engine still die when it's fully hot?
The EACV gets pretty hot, so it might be easier to unplug it while the engine is cold, then drive it until it's fully warm. Be aware that the car will not idle at all and will try to stall on you at every light. You'll need to use the gas pedal to keep it alive. The Check Engine light will come on also, but it'll go off again once you plug the EACV back in after.
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TeGGeR®

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Possibility, yes. And that dirt won't have been kind to your cylinder bores and rings either.

Sort of.

In the old days of carburetors, the throttle plate (the big round brass thing you see in the throttle body) was held open just a crack to allow air in when your foot was not on the gas. These days, the EACV (IAC) serves as an adjustable air bypass *around* the throttle, and the throttle plate is held completely closed when your foot is off the pedal.
You have about 5 or 6 controlled air sources for the engine to use (besides the throttle plate). All but one (the EACV) are concerned with a *cold* engine. When warm, all those sources should be closed except for the EACV. That your car won't idle at all with the EACV port plugged by your finger suggests that the other air inlets are fine and the EACV is stuck open. It is possible for grit to prevent the EACV from closing to the correct setting.
A cycling idle is normally due to a gross air leak into the intake, such as an EACV that is stuck open. The computer's #1 task is to keep the air/fuel mixture to a certain proportion, so faced with excess air that it cannot control, it will keep feeding fuel until the mixture is correct, which results in an increasing idle. It will only keep feeding fuel until it reaches certain internal limits. When it hits those limits, it will shut off the gas, the revs will fall, then the cycle repeats.
You can test this. Instead if covering the port completely, cover it slowly, sliding your finger over it bit by bit. You'll find a spot where the idle settles down. It may still be high, but won't fluctuate. Keep sliding your finger over it, and you'll find a spot where the idle is normal. That's how much excess air is entering.
It is possible to try to clean the EACV without removing it. Get a spray can of Throttle Body Cleaner. With the engine running, spray the Cleaner into the port you were covering with your finger. The car will stumble and attempt to stall. When it feels like it's about to stall, stop spraying and let the engine recover. Repeat.
Try the cleaner, then report back here.
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TeGGeR®

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Peter Koo wrote:

I decided to remove the EACV last night and after opening the device, I found the air opening to the EACV has a wire screen and the screen is almost 90% blocked with black carbon deposite. I proceed to clean the stuff out with a vacumn cleaner. After that, I used gasoline to wash the parts and also used the gasoline to wash inside the valve. After setting it dry, I dropped some lubricating oil into the valve opening to see if I can provide some lubrication for the valve. I put back the EACV and did a test drive but still find the Idel speed to be high and moving back and forth between 1000 to 1500 rpm. I decide to adjust the idel speed a little bit lower. After that, it kind of solve the problem. I need to do another test drive today to see if I really fixed the problem. I am kind of ticked off that when the car went in for 210,000 mile maintainence, the ideling was OK but because the guy forgot to tighten the Air intake boot which caused the dirt to get into the EACV which caused the ideling problem. These days, when you send you car for repair, you are taking a chance with a perfect good cars that comes back worse then it was then before. This has happen to me many times. I hope by cleaning the EACV valve will solve this problem and I will write a letter to that Acura dealer at Mission Viejo to let them know what they have done. I am pretty sure they reply will be how could I be sure that their tech. is the one that left it loose. All I can say is that good luck to all of you that need to rely on these guys and don't know how to check on their work.
Peter Koo
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<snip entire message>
You have not conducted my tests in order to determine that the EACV is operating properly.
The idle adjustment you performed may be masking a problem and not fixing it.
To correctly adjust the idle speed: 1) Warm car up thoroughly; 2) Make certain ALL accessories are off, including headlights; 3) Unplug EACV electrical connector; 4) Turn idle speed screw until idle speed is 650 rpm. 5) Plug EACV electrical connector back in. Idle should rise to 750.
You might have to shut car off and restart to see changes.
The first line up from zero on the tach is 500rpm. The next one is 750. The third is 1,000rpm.
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