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The Dreaded P0304 code
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=65&t=81294
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Author:  mnjeep4life [ Thu Feb 05, 2015 8:56 pm ]
Post subject:  The Dreaded P0304 code

Hey all,

I finally got another KJ! See here viewtopic.php?f=43&t=81153 for a sad story. I found another 07 Sport with
way too low of miles 58k and in way to good of condition. Bad new is she threw a CEL right away. I took it back to the Chevy dealership where I bought it.
Their techs found the P0304 code. Misfire #4. They proved the coil was good and changed the plugs. Still throwing the code. The sales manager told me to drive it for a few days and see if it fixes itself. Carbon build up? Sticky valve? So later I hopped in with it running and warm to find the CEL blinking. I knew that was bad. I shut it off and fired it back up. CEL stayed solid for a minute or two and started blinking again. When I rev it up the CEL goes solid again. The only time I can get it to blink is a long idle around 600 RPMs. Driving it stays solid. The motor seems to run fine. No loss of power. Might have a little more shake at low idle than my last KJ but all in all seems good. I plan on bringing it back to the dealership because I don't think its going to fix itself. Its an hour away and I got a busy work schedule. For peace of mind I changed the coil this evening and it did the same thing. I got a feeling that the grandma that owned it got the valves all carbed up and it's gonna need the heads pulled. Should I have a Jeep dealership look at it? I am a mechanic myself and I was driving me crazy to see the GM techs scratching their heads. I did find traces of possible mice but no sign of chewed wires.

The blinking CEL at low idle only is what boggles my mind. Anyone seen this before? Should I be driving it?

Author:  Billwill [ Sat Feb 07, 2015 8:21 am ]
Post subject:  Re: The Dreaded P0304 code

mnjeep4life wrote:
Hey all,

I finally got another KJ! See here viewtopic.php?f=43&t=81153 for a sad story. I found another 07 Sport with
way too low of miles 58k and in way to good of condition. Bad new is she threw a CEL right away. I took it back to the Chevy dealership where I bought it.
Their techs found the P0304 code. Misfire #4. They proved the coil was good and changed the plugs. Still throwing the code. The sales manager told me to drive it for a few days and see if it fixes itself. Carbon build up? Sticky valve? So later I hopped in with it running and warm to find the CEL blinking. I knew that was bad. I shut it off and fired it back up. CEL stayed solid for a minute or two and started blinking again. When I rev it up the CEL goes solid again. The only time I can get it to blink is a long idle around 600 RPMs. Driving it stays solid. The motor seems to run fine. No loss of power. Might have a little more shake at low idle than my last KJ but all in all seems good. I plan on bringing it back to the dealership because I don't think its going to fix itself. Its an hour away and I got a busy work schedule. For peace of mind I changed the coil this evening and it did the same thing. I got a feeling that the grandma that owned it got the valves all carbed up and it's gonna need the heads pulled. Should I have a Jeep dealership look at it? I am a mechanic myself and I was driving me crazy to see the GM techs scratching their heads. I did find traces of possible mice but no sign of chewed wires.

The blinking CEL at low idle only is what boggles my mind. Anyone seen this before? Should I be driving it?


Could be the #4 fuel injector or the wiring to #4 fuel injector. :?

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