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Unread 10-13-2011, 10:57 PM   #1
dustinv
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Join Date: Oct 2011
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misfire??

I have a 93 grand Cherokee Laredo with a 5.2 v8. More often then not it will run like it only has spark from 7 cylinders, maybe 6. When the trans shifts at 45mph it gets bad to the point where if I push the gas the whole jeep shakes and it has no power whatsoever. I've researched this online but nothing ever explains in depth. I have asked many many people about this its making my head spin. If anyone has experienced this or knows what could be causing it I need help! Any info or tips would be great. Thanks

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Unread 10-13-2011, 11:11 PM   #2
jnicewan
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1995 ZJ 
 
Join Date: Dec 2010
Location: Norman, OK
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Sounds like a possible secondary misfire concern. I would check things like the spark plugs and wires, cap and rotor. These things are considered normal maintenance/tune up stuff and should be changed periodically anyway. Oh and welcome to JF, have a look around and stay for awhile.
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Unread 10-14-2011, 11:37 AM   #3
dustinv
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Ill check them out and let u know. Thanks for the welcoming.
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Unread 10-17-2011, 10:51 AM   #4
dustinv
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Well I changed the plugs and it didn't change anything. The check engine light came on so I did the key trick and codes 14 (o2 sensor) code 27 (injector issue) and 32 were received. So seeing I know its an injector problem I started the jeep and unplugged the injector connectors 1 at a time. Each time I did this the motor would want to die. Good thing. Welp I got to #5 cylinder and it did nothing at all. I did it a couple times but still didn't change the act of the motor. Still runs rough. So knowing all this does it narrow it down to a certain issue?
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Unread 10-17-2011, 02:13 PM   #5
jnicewan
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1995 ZJ 
 
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Location: Norman, OK
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If you had a test light you could see if the injector gets power, and see if the PCM is commanding the injector to open. Keep in mind the other injector wire is ground by the PCM to control the injector so you would clamp the test light to B+ not ground. The light should blink pretty fast. Or you could swap the injector to another cylinder and see if 5 is good now and the misfire moves to the other cylinder. Other than that you might still need to verify you have good compression, maybe pull #5 spark plug and compare it to another.
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Unread 10-22-2011, 05:29 PM   #6
dustinv
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I changed the plugs and the one out of the #5 cylinder is more coffee color than the rest which are almost white with a haze. I used the test light on all the -injector plugs and it lit but didn't flash. Where would I go from here?
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Unread 10-23-2011, 01:51 PM   #7
jnicewan
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1995 ZJ 
 
Join Date: Dec 2010
Location: Norman, OK
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A working injector circuit will blink the test light with the engine running or at least while cranking. They make a little noid light that plugs into the injector connector, but a test light hooked to both terminals will do. If you suspect #5 and with the code you got, I would imagine you wont be seeing a blinkling light on that cylinder only. If that is the case you would have either a wiring problem or PCM problem.
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