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4.0 low idle

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Old 03-30-2012, 08:17 PM
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Default 4.0 low idle

My 4.0 97 idles low. Around 530-600. I replaced the iac it helped for like 15min any thoughts on were to look next?.
Old 03-30-2012, 10:00 PM
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Need to hook up to a scan tool and see what the desired idle speed is. How does it run otherwise?
Old 03-31-2012, 09:06 AM
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Pull the throttle body, and clean the IAC channel. It's probably clogged with crud.
Old 03-31-2012, 11:25 AM
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Its raining atm. Soo ill just stick a straw with some tb cleaners and spray it. I need to try something.
Old 03-31-2012, 12:11 PM
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Actually the crud buildup is in the channel where the IAC plunger travels. It will build up to a point that the IAC cannot adjust the idle properly. Eventually you'll get a P1294 (idle target not met) fault along with the very low idle. I wound up pulling the throttle body, and cleaning out the channel with a small wire brush attached to a dremel. I also took the time to give the TB a good cleaning (inside, and out) while I was at it since all sorts of crud built up on the edges of butterfly. You may want to also grab a TB gasket while you have the TB off. You're actually not far from me. I'm on the other side of the Raritan in Rahway. [waves]
Old 03-31-2012, 01:08 PM
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Your close. What jeep do you drive?
Old 03-31-2012, 03:24 PM
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Originally Posted by MSJeeps911
Your close. What jeep do you drive?
Yup, just up either Route 1 or to the end of Rt 27. I have a blue 02 WJ with a crazy looking antenna on the back.
Old 03-31-2012, 08:03 PM
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Originally Posted by KF2M

Yup, just up either Route 1 or to the end of Rt 27. I have a blue 02 WJ with a crazy looking antenna on the back.
Ive seen you.


Do you have a lift?. I have a black wj as well lifted 2.5in and 32s.
Old 04-01-2012, 09:31 AM
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Yeah I do get around. I can usually be found booming up and down the major highways of NJ for work. No lift though. Pretty much going to keep the Jeep stock this time around. Since it is my DD I can't afford spend alot of time and money messing with it. If I lifted it then I can't park in most parking garages in NYC as well since the Jeep is already too close to the ceilings in these garages.

Anyways how are you making out with the TB? The weather is going to be fairly nice today (the XYL has me doing yard work today). So I am stuck hanging around the house. If you do pull the TB I would suggest you get a new gasket for it.
Old 04-02-2012, 02:32 PM
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Cleaned it out. Didnt help
Ugh. All new gaskets too.
Old 04-02-2012, 08:46 PM
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My 95 4.0 idles around 600RPM.
Old 04-09-2012, 11:23 AM
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Sea foam?
Old 04-09-2012, 03:55 PM
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Just a word of warning to people that think you can use carburetor cleaner in your throttle body. Don't use throttle body (tb) cleaner like it says in a previous post.

I used carburetor cleaner before in a throttle body and it never would stay clean after that.

Does the rain or fog effect the idle either better or worse? Might be an egr valve? Just a guess
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