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Unread 08-10-2008, 03:27 PM   #1
caliskier
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Code P0304 Cylinder 4 misfire...help

I got the code P0304 which I believe is a Cylinder 4 misfire. I just replaced my plugs with the same recommended plugs. Which cylinder is cylinder 4? What could cause this?

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Unread 08-10-2008, 03:52 PM   #2
caliskier
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Actually, I found that the 4th cylinder is the middle left (passenger side). I guessed it was because the wire, or what ever that thing is called fit loosely over the plug. What could be the reason it won't spark?
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Unread 08-10-2008, 07:04 PM   #3
merlinTec
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Hi
Cylinder 4 in is the plug next to the gearbox not the middle. The lead is most likely the fault.
Regards,
Merlin
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Unread 08-10-2008, 07:21 PM   #4
caliskier
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Quote:
Originally Posted by merlinTec View Post
Hi
Cylinder 4 in is the plug next to the gearbox not the middle. The lead is most likely the fault.
Regards,
Merlin
Sorry, which one is that if I am looking at it from the front of the jeep? 3.7 V-6, also "lead" is that the deal that the piece that fits over the spark-plug?
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Unread 08-11-2008, 06:53 AM   #5
merlinTec
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LOL sorry thinking 2.4 so you have no leads just coils on the plugs so yes middle plug
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Unread 08-11-2008, 01:14 PM   #6
caliskier
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Quote:
Originally Posted by merlinTec View Post
LOL sorry thinking 2.4 so you have no leads just coils on the plugs so yes middle plug
Ok, so I have the right cylinder?

How do you diagnose the problem
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Unread 08-11-2008, 02:02 PM   #7
merlinTec
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Hi
You have done the plugs so ruled them out. Should have done compressions and cylinder leak test when the plugs where out but now the next test would be to swap the coil over with another cylinder and see if the misfire moves to that cylinder, if so then that coil is more then likely your fault.
Regards,
Merlin
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Unread 08-11-2008, 09:35 PM   #8
caliskier
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Quote:
Originally Posted by merlinTec View Post
Hi
You have done the plugs so ruled them out. Should have done compressions and cylinder leak test when the plugs where out but now the next test would be to swap the coil over with another cylinder and see if the misfire moves to that cylinder, if so then that coil is more then likely your fault.
Regards,
Merlin
Moved the coil reset the codes and I do not get a code, drove it around the block, no code, but the engine still sounds like it is missing. I am wondering if the plug is bad on cylindar 4. Is there a way to test coil w/o driving the car?
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Unread 08-12-2008, 07:01 AM   #9
merlinTec
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Hi
There is a misfire monitor test the dealer can do with DRB but other then that all you can do is use it as it can take some time to flag back up. You could disconnect the electrical plug on each injector one at a time to identify what cylinder is misfiring but this will flag up another code. You could also remove the plugs again and look for color difference on number 2 when compared to the others and then do compression test and cylinder leak test when you have the plugs out. Have you checked for air leaks?
Regards,
Merlin
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Unread 08-12-2008, 07:41 AM   #10
caliskier
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Quote:
Originally Posted by merlinTec View Post
Hi
There is a misfire monitor test the dealer can do with DRB but other then that all you can do is use it as it can take some time to flag back up. You could disconnect the electrical plug on each injector one at a time to identify what cylinder is misfiring but this will flag up another code. You could also remove the plugs again and look for color difference on number 2 when compared to the others and then do compression test and cylinder leak test when you have the plugs out. Have you checked for air leaks?
Regards,
Merlin

Thanks again...

Quote:
You could disconnect the electrical plug on each injector one at a time to identify what cylinder is misfiring but this will flag up another code.
I think I might try that

Quote:
You could also remove the plugs again and look for color difference on number 2 when compared to the others
Number 4?

Quote:
then do compression test and cylinder leak test when you have the plugs out.
I need a compressor for that right?, I don't have one.

Quote:
Have you checked for air leaks?
No, how is that done.

I was not worried about compression issues as he engine was running fine, the reason for the plug replacement was because it was overdue and wanted to improve fuel effeciency.

It was very difficult to pull the socket off the plug with each instal due to the rubber piece inside. I wonder if I cracked the plug pulling it off, I think I might pull #4 tonight and look at it.
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Unread 08-12-2008, 11:37 AM   #11
merlinTec
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If it's only has misfired after you changed the plugs then most likely faulty or damaged plug or incorrect cap. I was under the impression you did the plugs to fix the misfire.
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Unread 08-12-2008, 11:47 AM   #12
caliskier
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Quote:
Originally Posted by merlinTec View Post
If it's only has misfired after you changed the plugs then most likely faulty or damaged plug or incorrect cap. I was under the impression you did the plugs to fix the misfire.
Oops, should have been more clear. Ok, so cylindar 4 is the passenger side middle. I will pull the plug on it tonight and check, maybe some of the antiseze got on the plug and is gumming it up. I will try your other trick first though, I switched coil 4 w/ 1. Will start and pull the wire out of the coil on 1 to see if the engine sound changes. If it does then I know that it wasn't the coil and must be the sparkplug on 4. If it doesn't then it must be the coil and the spark plugs are all good. Have to run to the dealer anyway, I can drive over there on 5 cylindars and see if the code comes up.

Thanks for your help.
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Unread 08-12-2008, 01:12 PM   #13
merlinTec
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Hi
Don't pull the wires off the coils when it's running, this is bad practice as you get unburnt fuel going down the exhaust to the cat. I said the plug on the injectors.
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Unread 08-12-2008, 05:33 PM   #14
caliskier
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Quote:
Originally Posted by merlinTec View Post
Hi
Don't pull the wires off the coils when it's running, this is bad practice as you get unburnt fuel going down the exhaust to the cat. I said the plug on the injectors.

Oh, should have read that before I did it. Now I have error P 0351 which is a coil A malfunction. I was pluging in and unplugging the coil with the engine running, did it 3-4 times to hear the engine change. Wonder if I blew it.
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Unread 08-12-2008, 06:21 PM   #15
caliskier
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MerlinTec. Thanks for your time, I appreciate it. I pretty much wasted it. The car is fixed now, running fine.

Before I say this, I do have a degree in Mathematics.

I found my problem, don't know if I should say this as I am going to get ridiculed royally…..




I didn't put the damn spark plug in the hole.

"Hi, I'm the dumba$$!"
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