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  #25  
Old 05-09-2010, 09:58 PM
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Re: Misfires - '02 JGC Limited...

So maybe the next step would be to check the compression. When your engine is running smooth, then most probably all cylinders are working normally, but maybe the respective cylinder which is shown as misfiring has a lower compression and consequently lower output, what gives a slight deceleration what the PCM sees as a misfire.
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  #26  
Old 05-09-2010, 11:18 PM
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Re: Misfires - '02 JGC Limited...

i just bought a compression tool....

i have until the end of may to get this figured out...

ug..
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  #27  
Old 05-10-2010, 08:46 AM
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Re: Misfires - '02 JGC Limited...

Quote:
Originally Posted by Kpurintun View Post
i just bought a compression tool....

i have until the end of may to get this figured out...

ug..
A compression test is VERY easy to do. To prep, first you need to remove all your spark plugs. Then remove the power wire to the ignition coil (or disconnect all coil packs). Unplug your injectors so you don't have fuel sprayed into the engine. Also pull the throttle cable so the TB is completely open.

Screw the gauge into the spark plug hole of the first cylinder. Jump in the car and crank the car over 4 or 5 times. Record the reading from the gauge. Screw the gauge into the next plug hole and repeat. Finally, compare your numbers to the numbers Jeep gives.
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Old 05-11-2010, 06:00 PM
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Re: Misfires - '02 JGC Limited...

Just had same issue, combination of things happened. First off i need a new computer(pcm) it is running rich as can be and the sensors tell the comp to lean the engine out but it wont. i am missing on about 5 to 6 cyl at random. what i did is when it was missing i had no injector ground pulse from pcm on some injectors and some coils not getting ground pulse from pcm. dissconected battery took off unbolted pcm harness, put togather and the misfires switched to opposite sides of engine. anyway i need a comp. and becasue it was running so rich there was so much carbon build up, i had low compression on cyl#3. all others reading were 160-170psi
the #3 was first time 60psi then 70 psi. all missfires went away above 2000 rpms....weird.... jeep pcm has pre set determined values the pcm puts out at certain rpm ranges and thats why missfires went away above 2k rpms. i took off left head toook to maching shop and #3 valve needed a new valve job like somone else posted valvestem seal was leaking oil plus lots of carbon build up !!! looking at everything i can see the mess of carbon build up becasue engine running the richest it could for a long time and finally paid its toll on the head. it al stemmed from my computer so after head gets back from machine shop taking it to dodge to program new computer
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Old 05-12-2010, 04:08 PM
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Re: Misfires - '02 JGC Limited...

Machine shop just called me this afternoon, and another problem they found on the head is it dropped a valve guide so i am having all new valve guides installed as well
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Old 05-13-2010, 08:24 AM
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Re: Misfires - '02 JGC Limited...

Quote:
Originally Posted by j-lien View Post
Machine shop just called me this afternoon, and another problem they found on the head is it dropped a valve guide so i am having all new valve guides installed as well

ug!...

i am not sure... and i am probably jumping the gun...

but after like 6 or seven serious sea foam treatments... my wj pulls harder than ever. and it hasn't seen a misfire in over 50 miles. maybe it was just a shitty piece of carbon on a valve or something...

i haven't had the time to do a compression test. i have been traveling a lot.

ill let you know. i am gonna try to get the emissions test done today. if that works out.... WIN. if not... i'm crashing it into a bridge support.

kyle
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Old 05-13-2010, 09:38 AM
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Re: Misfires - '02 JGC Limited...

Thats awsome ! Hopefully your all good to go then.
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Old 05-13-2010, 09:56 AM
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Re: Misfires - '02 JGC Limited...

hopefully... crossing fingers, praying, wishing on stars....
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  #33  
Old 05-13-2010, 12:10 PM
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Re: Misfires - '02 JGC Limited...

IT PASSED!!! it still has a rough start... but it runs better. still no codes.

all i care about was the inspection... i was running out of time... thanks for your help guys!
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  #34  
Old 05-14-2010, 03:53 PM
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Re: Misfires - '02 JGC Limited...

Got codes again...
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  #35  
Old 05-14-2010, 03:55 PM
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Re: Misfires - '02 JGC Limited...

this time.... after i filled up with gas... 90 miles of starting stopping cold starts and everything... then a fill up... and BOOM rough and codes.. this is my favorite gas station. could it be bad gas? grrr!

kyle
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  #36  
Old 05-15-2010, 02:46 PM
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Re: Misfires - '02 JGC Limited...

When it is bad gas, you could expect the misfire in any cylinder. When it only happens with the same cylinder(s), i think you could rule out the gas itself. But very strange that you drove some time without messages and that it suddenly starts again. And the rough running is a sign that its really misfiring. Maybe some dirt in the respective fuel nozzle which partially blocks it?
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