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Old 01-25-2006, 03:02 AM   #1
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Consistent Idle problem, sputter @ idle-3000

I have read through tons of threads trying to figure out this probelm.

I've got a 95 wrangler with 2.5l

sometimes/most of the time when I start my jeep, idle speed will start out @ around 1500rpm then slowly go down to about 700-900(i beleive, or whatever is normal) then after a very short period of time(20 seconds or so) the idle will start to drop, and after about 10 more seconds gets down so low it feels like the jeep is going to stall... the engine then revs up all of a sudden to about 1100rpm then the process starts all over again....

now during this low rpm idle/almost stall. i can give it gas and the engine revs up, but wants to VERY quickly drop back down, if I were to try and take off, I virtually have no power, and if I push down on the throttle the engine will backfire like crazy... to the point of it going through the throttle body.. the problem will go away for a second then come right back, it will even come back in the middle of acceleration. even if I drive around for a while... the only thing i noticed is that, if I try to get on the highway, or any suspened higher RPM drive, then come to a stop the problem goes away(usually, not all the time)

I have read numerous threads on the egr valve, but it is only in effect when the engine gets up to temp... right? would a bad seal between intake/exhaust ports cause this? I recently changed the manifold gasket due to exhaust leak...

the problem is so consistent @ idle that I want to think electrical... my check eng. light goes off, and I get the 21 code, for O2 sensor, would the O2 sensor cause this? .... this problem happens a lot but the check engine light isn't always on, it usually doesn't come on until i have driven around a while...

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Old 01-25-2006, 09:28 AM   #2
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It could be the O2 sensor, but I'm more inclined to think it's a sensor like idle air control or map, maybe throttle position.

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Old 01-25-2006, 02:23 PM   #3
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It could be an O2 censor, but I wouldn't think it would be that drastic. I also don't think it has anything to do with the gasket you replaced, because it should hi rev all the time if you don't have that manifold sealed correctly.

I would think idle air control also.
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Old 01-25-2006, 03:30 PM   #4
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my only response is, how would tie into the backfiring issue, and the loss of power? I read that I can take off the throttle body to get to the IAC and clean it, so I will give it a shot...
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Old 01-25-2006, 07:05 PM   #5
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You could also try playing with the mechanical distributor advace and retard settings, new plug wires etc.
If there's a will, usually there's a way, but then you get to that bolt that you still can't get to with two extensions, two universal sockets, and a contorsionist midget trying to help you.

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Old 01-26-2006, 08:41 AM   #6
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If it's reading the air flow wrong and the engine is running lean it will "prefire" as opposed to running too rich and "postfire (backfire)". Check your plugs. Sooty and black/wet is rich, white is lean and a nice even tan is perfect. Mine runs lean constantly and I haven't been able to figure out why. It's so lean I get these white deposits on the plugs. It runs great though!

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