2004 4.0L Engine runs rough after sitting idle for more than 20 minutes. - JeepForum.com
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post #1 of 3 Old 08-22-2013, 06:20 PM Thread Starter
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2004 WJ 
Join Date: Aug 2013
Location: Conway
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2004 4.0L Engine runs rough after sitting idle for more than 20 minutes.

Hello all,
I am experiencing a rough running engine when I am sitting idle with the A/C on. First, the radiator fan went out about 3 years ago and I finally got it replaced. But before I got the fan replaced, I noticed that when I would sit idle and the engine temperature would go above 220 degrees the engine would start to run rough. I would shut the engine off and then try to restart but it would hardly turn over. I would have to smash the gas just to keep it sputtering. Most of the time it would try to run with a sputtering sound and then turn off. Now, I have replaced the radiator fan so the engine no longer overheats. It will sit idle and then follow the same symptoms like the engine was overheating but the temperature gauge showed that it was at normal operating temp. I turned the car off for about 15 minutes then tried to restart. It did the sputter start and would shut off. I would keep trying to start with my foot on the gas until it did start. I had to hold down the gas to keep it running and after about 30 seconds of pumping the gas, then engine would finally rev up. Only then would I be able to attempt to drive, but once i put it in to reverse or drive there is a clanking/ringing sound. The car will only go about 25 mph. It will finally go away after some driving and accelerate normally and wont happen again until I sit idle for a while. I have changed the spark plugs, got the spark plug coil checked, replaced radiator fan. Again, these symptoms only happen after sitting idle for about 20+ minutes. I do not have any issues while driving. Was thinking of replacing the Engine Crankshaft Position Sensor but I do not want to just keep replacing parts and the problem not go away. Any suggestions will be much appreciated.

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post #2 of 3 Old 08-22-2013, 07:09 PM
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2003 WJ 
Join Date: Dec 2009
Location: Ohio
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First its not a good idea to let it idle with the ac on that long, its not good for an engine. Second it sounds like vapor lock, where your fuel lines get so hot from idling that long it affects the flow of gas to your engine to the point of running roughly and misfiring, then as it cools it will run better. I'd suggest not letting it idle that long and I'm betting that will solve your problems.
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post #3 of 3 Old 08-23-2013, 10:13 AM
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You're welcome
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