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Unread 05-23-2015, 02:26 PM   #1
cconroy11
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2004 jeep liberty really bad misfiring

hey all,
So My jeep has a really weird issue its 2004 6cyl manual tranny.
It wont go over like...2,500 rpm, it drives and as long as you shift before 2.5 your ok.

I took it to a local parts store, and they ran a test, and basically cyl4 4 was misfiring and I had spark plug issues.

I replaced all 6 spark plugs, and the number 4 ignition coil, still the same problem... any ideas? could it be the coil wiring?

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Unread 05-23-2015, 03:37 PM   #2
WheelinKJ
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2003 KJ Liberty 
 
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is it running rough? engine light flashing?
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Unread 05-23-2015, 04:29 PM   #3
John Strenk
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It could be the wiring but I would borrow a compression gauge just to be sure the cylinder and valves are working OK.

All the spark in the world is not going to fire if you have no compression.
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Unread 05-24-2015, 12:52 AM   #4
cconroy11
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yeah its running rough and light is flashing
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Unread 05-24-2015, 11:02 AM   #5
streetglideok
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Light flashing means it's misfiring bad. If you put new NGK, or even Champion copper plugs in, gapped correctly, and you still have the misfire, then do a compression test on that cylinder and see what you measure. Also, are you 100% positive on cyl 4 location? I have seen that more than a few times where people misidentify a cylinder. You need 3 things to make the engine run, fuel, air and spark. If you have a bad misfire, you're missing one or more of those ingredients. Compression test will tell you if you have air to fire. Should be over 120psi, but you should check a couple of other cylinders to see what they measure at. 10% difference is the max allowable from lowest to highest. Do you have spark at that coil? With a stethoscope, can you hear the injector working, and does it sound just like the other injectors?
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Unread 05-25-2015, 05:21 PM   #6
WheelinKJ
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Dropped valve seat gave me the exact symptoms you're describing.
img_1106.jpg  
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Unread 05-25-2015, 06:50 PM   #7
cconroy11
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wow a valve issue...Ive never really messed with anything that intensive yet, seems out of my league, unless its easy to check/and or fix?
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Unread 05-25-2015, 07:07 PM   #8
WheelinKJ
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What caused mine is the previous owner let the engine get too hot due to a failed water pump. The aluminum head and steel valve seats expand at different rates sometimes causing them to literally fall out of the void their pressed into.

I'm not saying this is your problem, it could still be something else. This is what happened to me and others as well and your symptoms are spot on with how mine was acting.
If it is a dropped valve seat you will have zero compression on that cylinder. Remove the valve cover and look for the valve stem that is sitting lower than all the others. You may have to rotate the engine by hand to notice this. If it is a dropped valve seat, your head will have to come off and be taken to a shop.

I was lucky because the shop I went to happened to have a head from a dodge 3.7 that was ready to go. He charged me $50 cash and let me keep my old head (spare injectors, rockers, lash adjusters etc) and I had my jeep running later that evening.
It isn't really a tricky job but it is a long job with a lot of steps. The factory service manual is so detailed that if you follow it exactly you'll have positive results.

Also, if you end up driving it at all, be careful of your catalytic converter. A stuck open valve can cause unburnt fuel to be pushed out into the exhaust and be burnt off in the cat. This can cause the cat to glow red hot and possibly start a fire.
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Unread 05-25-2015, 07:08 PM   #9
streetglideok
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Quote:
Originally Posted by cconroy11 View Post
wow a valve issue...Ive never really messed with anything that intensive yet, seems out of my league, unless its easy to check/and or fix?
Suggest you re-read my post before you start condemning $1k and more in repair work. Unless you're content with paying someone to yank heads off, then I'll gladly open my hands for you
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Unread 05-25-2015, 07:13 PM   #10
02blue
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Cylinder 4 would be the middle one on the right side or passenger side for the US version KJ. The best thing would be to first take it somewhere for what streetglideok recommended if you can't do that yourself. Do it quick because if it drops then things that aren't supposed to meet will meet and very bad and expensive things can occur. Removing the head isn't terrible if you follow the FSM. Just a bunch of stuff in the way.
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Unread 05-25-2015, 07:14 PM   #11
02blue
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Quote:
Originally Posted by streetglideok View Post
Suggest you re-read my post before you start condemning $1k and more in repair work. Unless you're content with paying someone to yank heads off, then I'll gladly open my hands for you
I need to type faster
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