Poor idle of 4 cyl - JeepForum.com

 
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post #1 of 8 Old 04-22-2002, 07:53 AM Thread Starter
SnowMan
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Poor idle of 4 cyl

Does anyone else out there have problems with a poor idling with the 4 cyl. If so how did you fix it. I just put in new plugs, wires, cap. Fuel filter isn't that old and I just dropped in a fuel injector cleaner. Did a fuel pressure test and that's good. Always run the high test through it, don't know what's up. Any advice appreciated.


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post #2 of 8 Old 04-22-2002, 08:03 AM
Atropine
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please describe the poor idling...

93' YJ
00' TJ
02' KJ
04' Dodge Ram

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post #3 of 8 Old 04-22-2002, 09:09 AM
ArmyYJ
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AtRoPiNe,

You've always given me great advise on the mechanical mysteries of my 95 YJ 4 Banger, so I hope you don't mind if I chime in too:

Mine does the same thing, in idle the engine cycles high then low, not too much, but it's very noticable. This does not show on the RPM gadge and my highway, street, off road performance, and mpg does not seem to be effected.
I'm thinking the computer or the cat?

Thanks for all your help- you've already saved me $$$$ on a drive train-after lift-problem.

95 YJ 4 Banger
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post #4 of 8 Old 04-22-2002, 11:41 AM
4wheeler4CJ
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Hey Army,

Just a quick comment, I have seen that type of idling before, wher eit was simply something "wrong" with the computer module. Not wrong where it affected anything else, like mileage, performance, etc., just that the idle was a little erratic. It was left to be, since it was no big deal, and never caused a problem ever.

Just a note of encouragement, should it turn out to be the computer.
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post #5 of 8 Old 04-22-2002, 11:51 AM
ArmyYJ
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4Wheeler4CJ,

Cool thanks- I'm the first and only owner of this 95 YJ. I've used it as a farm tractor, shod horses out of the back of it for a few years, and drove it coast to coast twice. After 123,000+ miles it has become a real member of the family. I tend both beat it to death and baby it while trying to improve my repair/maintenance skills.

This forum has been a huge help. Thanks to all,

Keep it Jeep.

95 YJ 4 Banger
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post #6 of 8 Old 04-22-2002, 01:08 PM
4wheeler4CJ
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No problem, Army,

Most of us here try to help out. We are all learning, nobody can ever know everything <img border="0" title="" alt="[Wink]" src="wink.gif" />

This forum is definitely the best. There's a few "characters" on here, but they aren't fooling anyone, so we just let the diarhea-of-the-mouth go, LOL! <img border="0" title="" alt="[Wink]" src="wink.gif" />
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post #7 of 8 Old 04-24-2002, 07:55 AM Thread Starter
SnowMan
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Ya 4wheeler4CJ,

I hope that's the case. I get really good gas mileage 8km/L, which works out to about 18miles/gallon, nut bag. Just sometimes it shutters so hard that the whole jeep shakes and I think its going to stall then, it's back to normal idling around 500-600 rpm. Like you said there is no big jump in the rpm guage. Is there any way to check the computer for problems. My friend has one of those diagnostic computers, but the chrysler chip is about 150 bucks, should grab it up but I'd rather put some more stainless on.

Would also like to say that this site is great, I've only been on it for a week and have had several ideas given to me to enhance my jeeps performance and fuctionality. It's hard for canadians to get parts up here to with out paying an arm and a leg for the stuff at the jeep dealer (con artists), but thanks to this site I've already saved some serious cash. Agian thanks for all you jeepers help.

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post #8 of 8 Old 04-24-2002, 10:52 AM
Atropine
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Hmm...
I bet its going to be the oxygen sensor...

Idling high, then low, then high? These are noted to go bad and they match the symptoms you are having and this is why:

The oxygen sensor is located in the exhaust pipe right in front of the cat, and can detect rich and lean mixtures. The Oxygen sensor uses a chemical reaction that has voltage as a byproduct. The sensor has a tube made of ceramic zirconia. The zirconia generates voltage from approximately 1V in richer conditions to 0V in leaner conditions. The engine's computer looks at the voltage and determines if the mixture is rich or lean, and adjusts the amount of fuel entering the engine through the fuel injection system.

When the oxygen sensor is worn or broken, the computer does not know what your fuel/air ratio is, so it ends up guessing. Your car runs like crap and uses more fuel than it needs to. I was off roading and actually ripped mine completely out on a tree. The Jeep would idle real high, then real low , real high, real low. I though something was really messed up. I looked under and saw it hanging.

This is also up on my webpage under performance mods if you click the link.

Thanks for the compliment ArmyYJ!

93' YJ
00' TJ
02' KJ
04' Dodge Ram

"Jeep mechanic wanted: must be able to put square peg in round hole"
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