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Unread 09-06-2008, 07:24 AM   #1
johnboy2814
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Join Date: Nov 2004
Posts: 18
Cylinder Misfire

I keep getting a cylinder three misfire P0303 on my 05 liberty 3.7L(38,000mi.). We recently purchased it and I have replaced the plugs and coil so far. I did notice when changing the plugs that the plug in cylinder three was worn more than the others. The code sometimes turns the light on and will come back after a few days of resetting it. My next step is to do a compression check and leak down test. Any thoughts????????

Thanx

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Unread 09-06-2008, 09:30 AM   #2
nhcd538
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2001 WJ 
 
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Location: New Hartford, NY
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Well the first thing I'd suggest is changing the plugs and either swapping the #3 coil pack with another one of your packs or replacing it, which you have done. Unless there is a damaged wire somewhere in the coil pack #3 circuit (a possibility), you can pretty much rule that out. The more likely cause - these 3.7L engines have been known to need valve springs (even at low mileage), causing at first a misfire condition in the affected cylinder and then eventually loss of compression. When they do the compression test (which you should schedule ASAP) have them check the valve springs on the #3 cylinder. If you bought your Jeep new, valve springs and labor should be covered under your 7/70 warranty (correct me if I'm wrong?).

If you have the time (and you should make the time), read every thread on this page:

http://www.lostkjs.com/forum/phpBB2/...p?mode=results

You will be 100% educated on the subject and I guarantee it'll help you solve the problem or at least make sure the dealer doesn't screw you.
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Last edited by nhcd538; 09-06-2008 at 10:03 AM..
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Unread 09-06-2008, 10:29 AM   #3
jeepjeepster
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Change out the coils with another and see if it moves.

Checking the compression would be a good next step.
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Unread 09-06-2008, 02:48 PM   #4
johnboy2814
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Posts: 18
Misfire

Well doing some research appears that the valves were changed in the 05 models and cylinder misfires are common(thanx for the link above). Anyway did a compression check on cylinder 1 and 3, the reading on cylinder 1 was 190 PSI and cylinder 3 was 140 PSI. A difference of 50 PSI does not seem right to me??? I have also noticed a knock or valvetrain noise when the car is cold. Not sure if this is related or not but am very thankful that I signed over the 7/70 coverage now.
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Unread 11-20-2008, 04:05 PM   #5
johnboy2814
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b]UPDATE[/b]

Well since my last post I swapped injectors with cyliner 1 and the code still stayed with cylinder 3, also pulled the valve cover and found nothing abnormal.

So off to the dealer it went yesterday. They could not find a problem with cylinder three compression nor get it to duplicate. He noticed that I had autolite plugs installed and stated that they have had numerous problems with them. The only issue with that is I pulled the original plugs because of the misfire and they were Champions. Calls me back in the afternoon and states that he let it idle for a long time and he was getting multiple cylinder misfires, not enough in a row to set a code though.

They are recommending to do the fuel system flush and plug chage for the tune of $250.

In my mind I know this code is going to come back, but feel that I have to take this first step and when it re-occurs it doesn't come back until it's fixed.

Thoughts?????
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Unread 11-20-2008, 07:24 PM   #6
x99j
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Posts: 447
what is the misfire count at idle (on the drb 3)? if the missfire count is anywhere near 10 per minute tell them to quit sand bagging you!!!! and have them enact the tsb below to cure your problem! mike

LINK: TSB 09-007-06 page 1
http://ho*******cast.net/~merchjo/je...tsb-page-1.jpg
Page 2:
http://ho*******cast.net/~merchjo/je...tsb-page-2.jpg
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06 kj 3.7l, 6speed manual, np241 command track

91 yj 2.5l, ax-5, np 231 3 inck lift, 31'' mud rovers

12 kk 3.7L, 42rle, mp1522, d-30, 8.25.

Last edited by x99j; 11-25-2008 at 06:24 PM..
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Unread 11-25-2008, 05:35 PM   #7
johnboy2814
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Quote:
Originally Posted by x99j View Post
what is the misfire count at idle (on the drb 3)? if the missfire count is anywhere near 10 per minute tell them to quit sand bagging you!!!! and have them enact the tsb below to cure your problem! mike

LINK: TSB 09-007-06 page 1
http://ho*******cast.net/~merchjo/je...tsb-page-1.jpg
Page 2:
http://ho*******cast.net/~merchjo/je...tsb-page-2.jpg
Thanx for the links, I'm absolutely sure that is the problem now. I got it back last week and the code is already back, but the light is not on. The dealer could not duplicate the problem and updated the PCM instead. I'm going to change the plugs so at least they cannot say that's what causing it. As soon as the light comes on again, it's going back and I will tell them about this TSB.
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Unread 11-25-2008, 06:22 PM   #8
x99j
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good luck doing battle with the dealer! you are smart putting oem plugs back in. also it states in page one of the tsb that the cel MAY be on. it doesn't indicate it has to be on! also i believe 10 misfires a minute will not trip the cel! thanks for keeping us posted and let us know what happens! mike

Links went dead up top i tried re- pasting them but they won't take? my source still works though.

my source is below. the links are on page 2
http://www.dodgeforum.com/forum/show...gine+miss+idle

it is about a dakota owned by my company. mike
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06 kj 3.7l, 6speed manual, np241 command track

91 yj 2.5l, ax-5, np 231 3 inck lift, 31'' mud rovers

12 kk 3.7L, 42rle, mp1522, d-30, 8.25.
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Unread 01-08-2009, 02:11 PM   #9
johnboy2814
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Posts: 18
Just to update the post I had the TSB performed at the dealer about a month ago and the code has not come back since. They replaced all of the intakes valves and locks on both cylinder heads.

Thanx for the help
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Unread 04-24-2010, 11:14 AM   #10
1TONYRDZ
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Join Date: Apr 2010
Location: PEORIA, IL
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Misfire not from ignition

I've got my 2002 liberty 3.7l dismantled. Thought it was misfiring because of a spark plug or coil. Turned out to be a valve seat came loose and will not let the valve spring back up in the chamber on the cylinder head. I'm not really mechanically inclined, but i was not about to spend $4000 on a new engine. It is a costly process if you take it to an auto shop. I've got a mechanic working on it as a side job. The cylinder head has to be removed, but be careful, the timing has to be set before tearing apart. The intake manifold, valve cover, cooling fan, water pump, timing chain cover, exaust union, and alot of wiring have to be removed. The engine will work ok off and on, but trust me it can be worse than what i'm dealing with. If the valve does not spring back up it can break the piston head. So be sure you don't rev it up too much.
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