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Old February 10th 08, 11:40 AM posted to rec.autos.makers.honda
Tegger
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Posts: 1,716
Default 1990 Honda Accord Idle fluctuation

Paul Jr > wrote in
:

> On Jan 3, 7:04 pm, Tegger > wrote:


>>
>> Another air-related suggestion: When the car is warm and the idle is
>> fluctuating, remove the air cleaner pipe to the throttle body. Can
>> you progressively cover the throttle body with your hand to the point
>> where the idle settles down?
>>
>> What happens if you unplug the EACV? That's the idle air control
>> valve behind the throttle body. Sometimes a stuck-open EACV causes
>> fluctuating idle.
>>
>> And did you check the coolant in the rad, not the reservoir?
>>
>>
>>
>>
>>

>
> Yes, if I can cover the throttle body enough to set the idle down.




Bingo. You have a major air leak somewhere.


>
> I unplugged the EACV and the idle jumped up to a fast idle and the
> check engine light came on.




It is normal and expected that the CEL would illuminate when the EACV is
unplugged.



> I had to restart the car before the idle
> would settle down again (actually fluctuate again).




So the idle fluctuates even though the EACV is unplugged?

Hmmm.


>
> Does this tell you anything? Is the EACV the culprit?




You have large amounts of unwanted air entering the system.

Before anything else is done, you need to check each and every one of your
many vacuum hoses, including the ones inside the EGR control box on the
firewall.

You also have an Air Boost Valve. It is at the opposite end of the intake
plenum from the throttle body. With the engine idle fluctuating, disconnect
the Air Boost Valve's vacuum hose and plug the port in the valve with your
finger. If no settling of the idle, this part is OK.

Chek all the bolts/nuts that hold on the intake manifold and other intake
parts. Loose intake parts will leak vast amounts of air.


>
> Yes, I check the coolant levels and "burped" it also. I am very
> confident that there isn't any air in the coolant system.




If the coolant is right up against the bottom of the rad cap, then the
level is fine.

Your focus now is to find that air leak.

If you are 110% certain you have eliminated the possibility of any air
leaks, then -- and only then -- we try readjusting the idle speed screw.

What are these three digits of your VIN (represented here by x's? JHMCBxxx
(No personal information is in those three digits).



--
Tegger

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