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Unread 05-19-2009, 03:18 PM   #1
jtustaniwskyj
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2002 KJ Liberty 
 
Join Date: May 2009
Location: California
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intermittent misfire (P0306), 2002 Liberty 3.7L V6

I am having intermittent misfires with code P0306 showing up. The spark plug and coil have been replaced and it did not go away. When it happens I can shut off the engine and start back up with the misfires. A repair shop told me it was a head gasket but the compression is fine, pressurizing the cooling system shows no leakage into the cylinder, and no evidence of coolant getting into the oil (it is very clean). Any clues what it might be?

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Unread 05-20-2009, 09:45 AM   #2
DaveJKJ
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2005 KJ Liberty 
 
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FSM says causes are as follows. (05MY KJ FSM but it should be the same for this)

1) spark plugs

2) dirt in fuel system

3) burned, warped or pitted valves

4) faulty coil - (coil resistance should be .06-.09ohms primary and 6'000-9000 ohms secondary resistance.

That said, a buddy I wheel with has an 03 with codes 0305 and 0306 showing up intermittantly on #5 and #6. We swapped the coil paks, changed the plugs, checked and double checked coil pak wireing, etc and it still does it on occassion. He changed the gas brand too.

It runs just like it was a new vehicle so we don't think it is a valve or internal problem so we are stumped. We havn't had a professional look at it because it is running fine, so that's where we are with it. So if this thread turns up something I will be interested too.

Sorry if I didn't help with your problem, but that's where we are with his.
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Unread 05-21-2009, 03:24 PM   #3
2002jeepliberty
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Quote:
Originally Posted by DaveJKJ View Post
FSM says causes are as follows. (05MY KJ FSM but it should be the same for this)

1) spark plugs

2) dirt in fuel system

3) burned, warped or pitted valves

4) faulty coil - (coil resistance should be .06-.09ohms primary and 6'000-9000 ohms secondary resistance.

That said, a buddy I wheel with has an 03 with codes 0305 and 0306 showing up intermittantly on #5 and #6. We swapped the coil paks, changed the plugs, checked and double checked coil pak wireing, etc and it still does it on occassion. He changed the gas brand too.

It runs just like it was a new vehicle so we don't think it is a valve or internal problem so we are stumped. We havn't had a professional look at it because it is running fine, so that's where we are with it. So if this thread turns up something I will be interested too.

Sorry if I didn't help with your problem, but that's where we are with his.
ya i have a misfire in just cylinder 3 and its throwing me off cause i cant figure the ***** out,the jeep place said it was the intake valve but the thing i cant figure out is how do you determine that without taking the head off and looking at it? puzzles me
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Unread 05-21-2009, 05:25 PM   #4
richd
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They probably did a compression test.
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Unread 05-22-2009, 04:47 PM   #5
2002jeepliberty
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Quote:
Originally Posted by richd View Post
They probably did a compression test.
im bout to add some restore now haha
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Unread 05-22-2009, 06:43 PM   #6
DaveJKJ
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Quote:
Originally Posted by 2002jeepliberty View Post
im bout to add some restore now haha
Don't forget to rub the can real good 3x to let the genie out before you stuff him in your motor.....
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Unread 05-23-2009, 12:07 PM   #7
KMD
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vacume leak from intake perhaps.
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Unread 05-24-2009, 05:45 PM   #8
TJJP77
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Have you tried a cylinder leakdown test? It may not be a leaky head gasket, it may be a valve that isn't turning properly from carbon buildup/etc. If this happens, the shape of the valve head begins to take on a oval shape and it will no longer seal properly. A leakdown test that reveals hissing from the throttle body would be indicative of a bad intake valve.
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Unread 04-17-2015, 09:18 AM   #9
SIGP2101
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2006 KJ Liberty 
 
Join Date: Jun 2013
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After fighting this same issue for a year doing all possible and suggested I finally fix this problem by switching to 92 octane. Misfire gone forever and she purrs like cat.
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