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Solved High Idle - 91 Explorer Eddie Bauer

azrael_ak

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City, State
Wasilla, Alaska
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1991 Explorer Eddie Bauer
Is there anyone out there that can help me with a high idle problem?

The issue i am having is the engine kicks from normal idle (800ish rpms) to a very high idle (1800 rpms) for no reason. I know on some cars you can hear it click and it idles up a little bit but nowhere near like this problem.

I have replaced the Idle Air Control Module (went thru three of those to rule it out, also tested the jack with a multimeter), the Mass Airflow Sensor, the TPS, the PCV valve. I'm running out of ideas on what it could be.

Any help would be greatly appreciated.

A clerk at napa said something about a MAP control unit? But i don't know enough about it to say.

This problem is killing my gas consumption rate as well. My trip meter says 55 miles and i am a little over a half a tank. With winter coming and having to warm it up every morning, i would like to get this fixed asap

Thanks :)
 


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Rhett

Let Them Eat Cake
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94 Sport 4x4
I think I'd try some easier cheaper things before I replaced the MAF sensor.

Are you sure you don't have any vacuum leaks? That can cause irregular idle, and if the FPR vac line is broken, I can see that causing low mpg.

How about the throttle cable -- is it binding? Check near the gas pedal, and near the throttle body. Also make sure the throttle plate (in the throttle body) is not gummed up with carbon. It should move easily with no obstructions.

Sometimes the a/c compressor will get stuck on, and the extra load will idle it up, too. Usually you can hear the compressor clutch popping off and on in that case.
 




azrael_ak

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1991 Explorer Eddie Bauer
Don't hear anything out of the ordinary. Did a vacuum test and its normal. The only thing that you posted that sounds familiar is sometimes i go to leave and push the gas pedal and it seems to be hanging up. But i don't think its related. The idle thing happens by itself for no reason. Yesterday i was watching it and it was sitting at 850rpms and it just clicked and jumped up to 1800. then i noticed it would sometimes click and go back to normal for about 3 seconds...then jump back up.

So something is telling it to jump up. It usually happens after it warms up a little. Never does it while its cold.

Currently my air conditioner isn't charged. Think that would cause something like that? I had a leaky adapter on the A/C dryer cannister and had to find a replacement. I think tomorrow i will put on the new adapter and recharge the system. I don't think its related. I've watched it with the hood open and the clutch on the A/C pump doesn't engage when it happens.

Been beating my head against the wall for almost a year on this problem.
 




Centaurious

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1994 Explorer Sport
I would clean the throttle body/butterfly, test the Throttle Position Sensor for smooth readings when operated, remove the EGR Valve from the intake and ream out the carbon in the passage behind it and I would check the codes for any clues
 




azrael_ak

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1991 Explorer Eddie Bauer
Will try that. No codes. Checked for those first. I replaced the throttle position sensor earlier this year. It had smooth movement. But i will check it again. Tested everything with a multimeter and everything checks out. I will clean the EGR tho, I didn't think of that one.
 




Centaurious

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That passage behind the EGR stumped me for a couple of days when I got my 94. It's about 1/2" or 13mm and mine was completely solid with carbon. In my experience these sudden changes that revert themselves are almost always electrical or electrical related. In order to affect the idle it must either relate to Fuel, to Air, or to Timing. Something as simple as the Charcoal Canister Purge Valve can affect the engine running if say the Charcoal Canister was damaged, thus allowing extra un-metered air into the engine at highway speeds.

Best of Luck
 




Rhett

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Currently my air conditioner isn't charged. Think that would cause something like that?

For sure, yes. The clicking you hear is the a/c compressor clutch cycling, trying to maintain pressure with what little refrigerant is in there. You should not be seeing a jump to 1800 rpm, that means the compressor clutch is putting a bigger load than normal on the system. It may be wearing out. Try charging it (relatively cheap to do) and see if it improves.
 




azrael_ak

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1991 Explorer Eddie Bauer
I tried charging it but i found that the high pressure A/C line is damaged and i will have to save up to replace it. Had to use a leak detector kit to find out where it was leaking but i did. I never did see the pump kick on.
 




Dora 1993

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If the AC is related but you don't want to fix it right now you can just unplug the compressor for now until spring. Then your idle won't go nuts when its warming up.
 




azrael_ak

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1991 Explorer Eddie Bauer
My brother figured out the problem. The mass airflow sensor that i purchased new from Napa died after being in the car maybe two weeks tops. Thank you for all of your suggestions.
 




Centaurious

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I would wonder why it died. Are you running a K&N oiled type air filter that might have contaminated it?
 








azrael_ak

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1991 Explorer Eddie Bauer
Yes I am running a K & N air filter but its been in the car for about 3 years with no issues. I don't think that would be the cause. The more likely cause is someone bought it....then returned their broken one. It's the oldest scam in the book. I was in a AutoZone recently and was getting an air filter. Someone had purchased a K & N filter for their vehicle. Then returned the K & N box with their crappy used paper filter which looked like it was at least 5 years old, in the K & N box. Was about 100$ that they had to eat because they didn't check the box when it was returned. I suppose they have no way in testing mass airflow sensors.
 




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