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Unread 06-20-2011, 07:28 PM   #1
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2008 KK Liberty 
Join Date: May 2011
Location: Wareham, MA
Posts: 3
P300 code

I hope someone can help, I bought a 2008 Jeep Liberty a month ago from a dealership. Since the day I drove it off the lot it has been running rough at idle. The CEL has been coming on intermittently with a P300 code. The dealership has change an O2 sensor, and plugs. Every time I bring it back they tell me that they don't see anything wrong with it. I'm not sure if it's relevant, but it rained really hard the other night and it's been running even worse since then. Has anyone had any similar experiences like this. Its a 3.7 automatic, with 42,000 miles on it. When I purchased it, it had 39,900. Any advice would be greatly appreciated.

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Unread 06-20-2011, 08:13 PM   #2
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1995 YJ Wrangler 
Join Date: Oct 2009
Location: oklahoma
Posts: 118
p0300-multiple cylinder misfire. pull the coils off the spark plugs and look for water intrusion.
95 yj
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Unread 04-14-2012, 10:28 PM   #3
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Join Date: Mar 2012
Posts: 21
Hope you don't have broken valve retainer springs like mine (or valve-lock as some call it). I bought a 02 liberty with 3.7 motor with 27,000 mi on it (remanned long block) drove it 3 days and started running rough and then diddnt want to stay running at all. Called a diagnostic expert and he garanteed me that he new the problem. A very long story short turned out he was right. Basically need a new motor cost about 3000 plus install about same. I know cuz the papers were still in the glove box from the last owner having same problem. Thanks mopar. Still love the paperweight tho ;-) so after I fix it. This will be the 3rd motor in vehicle...all the best of luck to you.
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Unread 04-14-2012, 10:37 PM   #4
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Join Date: Mar 2012
Posts: 21
Same code mine shot and I had 2 intake spings broken and 2 valves locked. One went first and it would still run but roughly. Kept driving it and another went accept when this happens you lose compression on that cylinder thus making it ineffective so I was driving around on 5 cylinders and then once the second lock-up occurred I went to a 4 cyl and she don't want to run that way so out of commission she is still not fixed. Don't know if I want to put all that time in on a gamble if the pistons may have hit valves therefore bending them making thing resemble paperweights. Lol. Fml
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