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Another unsolvable misfire

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Old 08-31-2016, 08:09 PM
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Default Another unsolvable misfire
On my 96 xj ive had a misfire that i could not get to go away. Today i did a compression test and cylinder one only had 50 psi. The jeep misfires terrible on that one cylinder, knocks, pops, and stumbles. Hovever if i loosen the exhaust rocker up about three turns it doesn't sound or skip as bad. What is my problem?

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Old 08-31-2016, 10:00 PM
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Originally Posted by $200xjbuild
On my 96 xj ive had a misfire that i could not get to go away. Today i did a compression test and cylinder one only had 50 psi. The jeep misfires terrible on that one cylinder, knocks, pops, and stumbles. Hovever if i loosen the exhaust rocker up about three turns it doesn't sound or skip as bad. What is my problem? Thanks
did u determine why there's low compression? Did u perform a cylinder leak down test yet?
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Old 08-31-2016, 10:05 PM
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Originally Posted by XJwonders
did u determine why there's low compression? Did u perform a cylinder leak down test yet?
Yes i did, its leaking out the exhaust valve. When i loosen the rocker it doesn't leak as bad.
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Old 08-31-2016, 10:25 PM
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Originally Posted by XJwonders
did u determine why there's low compression? Did u perform a cylinder leak down test yet?
Is it possible the timing jumped? Either on the dizzy or cam?
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Old 08-31-2016, 10:28 PM
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Originally Posted by $200xjbuild
Is it possible the timing jumped? Either on the dizzy or cam?
if that did, then all the cylinders would be misfiring
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Old 08-31-2016, 10:29 PM
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Originally Posted by XJwonders
if that did, then all the cylinders would be misfiring
Thats what i figured.
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Old 09-01-2016, 07:58 AM
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stuck valve?
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Old 09-01-2016, 08:12 AM
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excessive carbon build up on the valve causing it to not seat. I would see if you could do a steam clean on it an try to break it off that way. there is write up on it right here, https://www.cherokeeforum.com/f30/st...-4-0-a-226299/.
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Old 09-02-2016, 01:16 PM
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Originally Posted by dans98xj
excessive carbon build up on the valve causing it to not seat. I would see if you could do a steam clean on it an try to break it off that way. there is write up on it right here, https://www.cherokeeforum.com/f30/st...-4-0-a-226299/.
Cleaned the valves, no difference.
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Old 09-02-2016, 04:05 PM
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Originally Posted by $200xjbuild
Cleaned the valves, no difference.
Looks like you'll be pulling the head off then.
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Old 09-02-2016, 04:18 PM
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Originally Posted by cruiser54

Looks like you'll be pulling the head off then.
Whats odd though is that yesterday i put about 3 tablespoons of oil in the bad cylinder and it ran fine for a three hour drive, after that it started running like junk again. Also what should timing advance be at idle?
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Old 09-02-2016, 04:21 PM
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Originally Posted by $200xjbuild
Whats odd though is that yesterday i put about 3 tablespoons of oil in the bad cylinder and it ran fine for a three hour drive, after that it started running like junk again. Also what should timing advance be at idle?
that sound like your piston rings are worn out. Time to replace them
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Old 09-02-2016, 04:23 PM
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Originally Posted by XJwonders
that sound like your piston rings are worn out. Time to replace them
The jeep doesnt burn any oil at all.
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Old 09-02-2016, 04:23 PM
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Originally Posted by $200xjbuild
The jeep doesnt burn any oil at all.
I have exact same thing happening on my jeep. The oil ring is intact but the compression rings are worn out
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Old 09-02-2016, 04:26 PM
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Originally Posted by XJwonders
I have exact same thing happening on my jeep. The oil ring is intact but the compression rings are worn out
I should also note that the jeep has perfect compression on the 5 other cylinders.
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