P0204 & P0304 Codes - JeepForum.com

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post #1 of 5 Old 01-01-2014, 06:26 PM Thread Starter
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P0204 & P0304 Codes

My Jeep is an 02 Wrangler 4.0L automatic, with the following modifications: 4" suspension lift, 1" body lift, Curry Industries Ford 9 Front and Rear axles w/ disc brakes, ARB air lockers, and 456 gears. It's not a daily driver and is only driven for fun, currently has about 42,000 miles. I took it out the other day and out of the blue it started to hesitate at about 2800 rpms and the check engine light started to blink. It feels like the engine isn't getting gas and then gets it back again. I checked the codes and got P0204 and P0304. Misfire in cylinder 4. Here's what I've done to try and correct the problem. So far none of this has fixed it.

1. changed out all spark plugs
2. replaced coil rail
3. replaced fuel injector in #4
4. replaced fuel injector plug in and short piece of wire for injector #4 (something had chewed the wire at the injector plug in)
5. added seafoam to fuel tank to clean injectors

When I disconnect the battery the codes will clear and it appears to be fixed until I drive it for 2 or 3 miles and then it's back again.

At this point, I'm stumped. Any suggestions would be greatly appreciated.

JMW26 is offline  
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post #2 of 5 Old 09-02-2015, 12:38 PM
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Did you ever find a solution to your issue?
I'm having exactly the same problem on my 06 TJ 4.0
Any help would be great!
Oncenter is offline  
post #3 of 5 Old 09-03-2015, 03:44 AM
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2003 TJ Wrangler 
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Good place to start.

Originally Posted by mrblaine View Post
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Back into my Jeep... finally.
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post #4 of 5 Old 09-03-2015, 05:29 AM
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1998 TJ Wrangler 
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Location: Cedar Rapids
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Another place to check codes is https://actron.com/code-lookup
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post #5 of 5 Old 09-03-2015, 09:17 AM
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I appreciate the Code sites, Thanks, But I have the exact same problem as JMW26 did last year. It all started with a rat eating the wire at the injector plug, started running rough of course, engine light etc. replaced the connector, the problem did not go away. Erased the code, did all the things JMW26 did above, same issues...
Oncenter is offline  

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