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Unread 05-13-2010, 04:09 PM   #1
budro69
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Code P0304?????? What do I do?????

My wife's 03 GC, had a spurt of bad behavior this afternoon. She was merging on the freeway and it began to bog and almost stalled when she about hit 70. She pulled off and it idled normal but the engine light was flashing. She called me at work and I told her to turn it off and restart it, from there it ran fine but instead of flashing the engine light just stayed on. I had her check her codes and it came up with a P0304, I couldn't find the trouble code list but thanks to a previous post and ezflip I discovered it was a #4 cyl. misfire. I don't really know what could cause this and I was hoping someone on here would have some prior knowledge that might help me out. Any help or advice would be greatly appreciated. Thanks ahead of time.

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Unread 05-13-2010, 05:44 PM   #2
mighttuss
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Well for starter my friend you need a trun up! If you are not a do it your selfer,then maybe one of your friends is. If you lived in KY I would help you. Write down the make and model of your automoble take the list to your autoparts dealer and get Spark plugs/ Spark plug wires / R-cap and button. And yes I buy them all,cause you might have someone to tell you its your spark plugs and get home and change them and start you jeep and it do the same thing it did before. So why not change it all why your under the hood.
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Unread 05-14-2010, 05:40 AM   #3
budro69
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I wouldn't say I am a mechanic by any means but spark plugs and wires I can usually handle. Although her car is different than anyone I have ever worked on. All the spark plugs are under this bar thing, and I see no distributor anywhere. I will take your advice and buy those things and change them, I'm fairly sure when I get them I will see where they go. Thanks for the advice mighttuss.
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Unread 05-14-2010, 09:52 AM   #4
oldfamilyguy
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The bar thing is the coil assembly, no distributor. take it off to get at the plugs. change them all if it hasn't been done in a while, especially look at #4 it might be obviuosly bad. There are other causes for a misfire, but go with the plugs first.
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Unread 05-14-2010, 11:38 AM   #5
BigE3
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Normally if its just one bad cylinder. You can be sure either a plug or wire is bad. I would check the wire 1st and see if you see any burn marks on the plastic. That will tell you that the insulator is bad and electricity is searching for the nearest ground.
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Unread 05-14-2010, 12:10 PM   #6
rm2001wj
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FYI for some of you posters; WJs (99 and later Grand Cherokees) use coil on plug ignition systems with no distributor and no spark plug wires. oldfamilyguy is right on target.
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Unread 05-17-2010, 04:54 AM   #7
budro69
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Thanks for the help, I am picking up new plugs this week
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Unread 05-17-2010, 04:57 AM   #8
MacK
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My 2007 JK did the same error, P0306. I installed new spark plugs and wires and it has been great ever since. Even runs smoother.. good luck!
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