2004 4.0 Misfire - JeepForum.com
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post #1 of 4 Old 11-27-2009, 07:07 AM Thread Starter
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2004 WJ 
Join Date: Nov 2009
Location: CT
Posts: 2
2004 4.0 Misfire

I have a Grand Cherokee, 4.0L, 89,500 miles. About six months ago, I was on the highway when it misfired, check engine started flashing. I immediately got it to the dealer who diagnosed cylinder misfire #6 and "fuel injector cuts out electrically". PCM was replaced.

All was well until recently, when I started to notice an occasional rough idle. Then it happened, again, cylinder misfire and flashing check engine. The dealer said the code was P0305B, cylinder #5 misfire, and said it may have attributed to bad gas. Filled the tank, added dry gas, injector cleaner, and was fine for a couple of days when the same thing happened. I then brought it to a different shop. He pulled up the P0305B code and P0205 injector circuit cylinder #5. The injector resistance, wiring and pulse were checked with no problems. Throttle position sensor was checked and found to be OK. He suggested it was a possible bad PCM and to go back to the dealer, which I did. The PCM was under warranty, so he replaced it. Picked it up, drove it, and again, cylinder misfire and flashing check engine.

It starts fine, the problem seems to occur when the engine is at operating temperature after a warm start. I'm reluctant to go back to the dealer.

Any ideas?

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post #2 of 4 Old 12-01-2009, 10:56 AM Thread Starter
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Join Date: Nov 2009
Location: CT
Posts: 2
I went to another dealer, he de-carbed the valves, ran like a top for a while, and then another misfire with a flashing CEL. Any ideas? O2 sensor? Bad injector or wiring? Any help/advice would be appreciated...thanks.
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post #3 of 4 Old 12-01-2009, 11:10 AM
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1998 ZJ 
Join Date: Dec 2007
Posts: 8,204
Have them check the wiring, my buddy with a 2004 is having this same issue right now and has done all the fixes you have but it still throws the code and idles weird.
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post #4 of 4 Old 06-16-2015, 01:40 PM
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2004 WJ 
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It is a exhaust valve issue with mine on 3rd and 4tg cylinder, pull the valve cover and rockers and try to see if there is an issue with contact between valve and rocker arm. A straight line on the top of the valve stem means it isn't properly adjusted. The service on all data also says to check retainers but that doesn't seen to be an issue with these engines. Also after adjustment and reassembly clean engine with sea foam due to issue being caused by a carbon build up on valves.. Maybe this will help
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