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Old 02-20-2012, 10:22 AM   #1
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Rough Idle help

I have a 2002 TJ with a 4.0....IT has a little bit of a rough idle. Nothing bad, but just slightly rough. IT has 70,000 miles on it. I took the Throttle body off and cleaned it the TPS and the IAC. I also changed the plugs and put seafoam in the gas. I still have a rough idle. Any other ideas of things i can do??

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Old 02-20-2012, 11:30 AM   #2
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Plug wires? an easy way to check raise the hood at nite and look for sparking. Much better than gettin bit. or bad gas

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Old 02-20-2012, 11:33 AM   #3
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2000 and newer have no plug wires
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Old 02-20-2012, 11:59 AM   #4
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2000 and newer have no plug wires
Learn something new everyday. Coil Packs I guess?
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Old 02-20-2012, 12:16 PM   #5
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That's right, well actually they switched over at mid year 1999
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Old 02-20-2012, 12:29 PM   #6
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I was thinking possibly and O2 sensor???
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Old 02-20-2012, 12:47 PM   #7
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Had bad gas mileage?
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Old 02-20-2012, 02:04 PM   #8
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Nope...getting between 18-20 mpg... I have had a few emissions codes( P0442, P0455, P0456). Checked all of the EVAP lines and fuel lines. Can't find any leaks. Replaced gas cap. it is odd to me that my gas mileage is still really good.
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Old 02-21-2012, 06:57 AM   #9
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Bump...
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Old 02-21-2012, 07:02 AM   #10
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You said you were thinking 02 sensor try unplugging it and see if it runs any better, when you unplug it it will run off of the computer presets. Does it idle rough all the time when its cold and warmed up
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Old 02-21-2012, 07:27 AM   #11
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You said you were thinking 02 sensor try unplugging it and see if it runs any better, when you unplug it it will run off of the computer presets. Does it idle rough all the time when its cold and warmed up
won't it run worse if you do that?

o2 sensor is part of regular maintenance that commonly gets overlooked (me too). I think they should be changed out ever 75k to 100k. I have 117k on mine, and its hasn't been changed.

I had a pretty rough idle and it ended up being my #5 plug. After I changed my plugs, it obviously ran a lot better.

It really depends on you and how rough your idle is. It wouldn't hurt to check your coil packs and possibly change out the o2 sensor. Good Luck!
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Old 02-21-2012, 07:31 AM   #12
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won't it run worse if you do that?
No it won't run worse if you unplug it. It runs worse with it plugged in feeding the computer the wrong information.
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Old 02-22-2012, 07:12 AM   #13
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No it won't run worse if you unplug it. It runs worse with it plugged in feeding the computer the wrong information.
ya, guess ur right.

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