Rough idle -
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post #1 of 5 Old 09-03-2013, 11:57 PM Thread Starter
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Join Date: Feb 2008
Location: Salinas CA
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Rough idle

I need to pick your brains for this one. I have a 2002 Renegade with a 3.7L with approx. 135k. One day it started running rough like it was missing real bad. While trying to accelerate, it started shuddering and hesitating with a severe lack of power. The Check Engine light came on. After stopping and checking that the engine was still there, I was able to start it back up and drive it home with no problems. I was able to read a P0304 "cylinder 4 misfire" code. Since then, I have replaced the #4 coil pack, all spark plugs (champion copper) crank position sensor, cam position sensor, IAC valve, the battery, and the #4 injector. I also replaced the fuel pump and filter, completely cleaned out the tank. It only runs rough when it is started cold. After the engine is warmed up and is allowed to be shut off, then when it is restarted it runs very smooth and with plenty of power. Any ideas would be greatly appreciated!

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post #2 of 5 Old 09-04-2013, 09:45 PM
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Someday, I will get my Cherokee back! LOL!

Last edited by 56Mercgal; 09-04-2013 at 09:57 PM.
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post #3 of 5 Old 09-05-2013, 07:05 PM
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2002 KJ Liberty 
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Do a compression test and look in particular at the #2 cylinder. The early 3.7 engines drop a valve seat (mine was the intake) in the #2 cylinder around 138K.
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post #4 of 5 Old 09-05-2013, 07:08 PM
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2002 KJ Liberty 
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Also pull out the intake air temp sensor and see if there is any oil on it. Cleaning it off either way will only help you.
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post #5 of 5 Old 09-05-2013, 07:12 PM
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2002 KJ Liberty 
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One other thing, when I took my head off to find the cause of my engine's "death" I found alot of carbon on the pistons and the inside of the head. Get the carbon removed and you could avoid alot of headaches!
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check engine light , p0304 , rough idle

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