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Rough/Choppy Idle sometimes

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Old 08-19-2014, 08:21 AM
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Default Rough/Choppy Idle sometimes

Doesn't happen all of the time but occasionally I will get a rough idle. Doesn't matter if jeep is warm or cold and it's most noticeable while in gear at a stop light or something. Once i accelerate, it runs fine. No hesitation when accelerating either. I know it's a pretty broad question but where should I begin?

98 Classic 4.0 I bought the jeep with 116000 and now has about 143000. PO claimed to have done a recent tune up.

Last edited by rgr4475; 08-19-2014 at 08:25 AM.
Old 08-19-2014, 05:33 PM
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Any ideas? Should I start with the basic plugs, wires, cap and rotor? Fuel filter? I just don't want to start throwing money at it if there is a better option of narrowing the problem down.
Old 08-19-2014, 05:37 PM
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Clean the throttle body especially the IAC.
Old 08-19-2014, 08:53 PM
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Originally Posted by Rockfrog
Clean the throttle body especially the IAC.
Will do, thank you.
Old 08-20-2014, 07:10 AM
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I'd start with cleaning IAC and throttle body. There are a few other causes, but start with this simple/free stuff first.

Regarding your tune-up, depends on when this was done the last time. If "cant remember" or " no idea", do a tune-up. Good (preventative) maintenance anyway.

Let us know how you go.
Old 08-20-2014, 11:18 AM
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I had something similar with my Jeep, the idle would pulse a little bit at lights. I just added some fuel injector cleaner on my next fill up, so far its been holding steady.
Old 08-20-2014, 01:45 PM
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Originally Posted by Roler
I'd start with cleaning IAC and throttle body. There are a few other causes, but start with this simple/free stuff first.

Regarding your tune-up, depends on when this was done the last time. If "cant remember" or " no idea", do a tune-up. Good (preventative) maintenance anyway.

Let us know how you go.
Thanks, I will start with that. I'll be doing this weekend and will post up how it went.
Old 08-20-2014, 04:41 PM
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Good on ye, mate. Will keep an eye out.
Old 08-20-2014, 09:55 PM
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Oh! Is it okay right now? I also got similar problem.








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Last edited by siuling337; 08-31-2014 at 04:57 AM.
Old 08-21-2014, 12:08 AM
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Originally Posted by siuling337
Oh! Is it okay right now? I also got similar problem.
The rough idle is intermittent. Drives fine though.
Old 08-31-2014, 03:11 PM
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I got to this a weekend later than I wanted to. But here are some before and after pictures. As you can see it really needed a cleaning. Everything seems to be smooth at the moment but haven't driven it too much yet. Based on how dirty this was I'm guessing this was the culprit. Thanks for everyone's help!








Last edited by rgr4475; 08-31-2014 at 03:32 PM.
Old 09-01-2014, 04:34 AM
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Excellent work on those.
I might steel your pics because they make good examples, if you don't mind.

Last edited by Roler; 09-01-2014 at 04:36 AM.
Old 09-01-2014, 08:16 AM
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Originally Posted by Roler
Excellent work on those.
I might steel your pics because they make good examples, if you don't mind.
Thank you. And absolutely, feel free to do what you wish with the pictures.
Old 09-01-2014, 08:51 AM
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Makes me want to go clean my TB and IAC just for ease of mind..
Old 09-01-2014, 09:11 AM
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Originally Posted by JeepMN
Makes me want to go clean my TB and IAC just for ease of mind..
I hear ya. If you haven't done it, it's ridiculously easy and quick to do.


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