Random or multiple cylinder misfire help!!! - JeepForum.com
 
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post #1 of 5 Old 07-13-2017, 09:21 PM Thread Starter
zjmike97
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1996 ZJ 
 
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Location: Freedom
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Random or multiple cylinder misfire help!!!

New to the forums and need some help diagnosing my current misfire issue! I have a 1996 ZJ with the 4.0L and have been fighting with it to figure out the cause of a bad misfire it randomly started having. It has a P0300 for random or multiple cylinder misfire and each cylinders misfire code. So far I have replaced the plugs, wires, cap, rotor button, ignition coil, distributor pick up coil, crank positioning sensor. I also checked vacuum pressure, fuel pressure, drained gas, replaced fuel filter, and put in fresh gas. Checked through what I could of the wire harness for broke wires and checked all grounds. STILL cant get rid of this misfire. It seems to have really good spark from the ignition coil and cylinder 1 but get weaker as you go from cylinder 2 to cylinder 6 with 6 being the worst. I really havr no idea what to try next other than possibly the PCM. Anyone else have this issue or have any ideas?

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post #2 of 5 Old 07-13-2017, 09:35 PM
kg6mov
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1996 ZJ 
 
Join Date: Nov 2012
Location: Cupertino
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All mopar sensors right?


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post #3 of 5 Old 07-14-2017, 05:47 AM
Marcos
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1993 ZJ 
 
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Location: Germantown
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Odd that the spark would get progressively weaker like that. Any side play in the distributor shaft? Loose shutter plate?
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post #4 of 5 Old 07-14-2017, 06:49 AM
AVR2
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2002 WJ 
 
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Have you checked compression to rule out mechanical issues in the head?
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post #5 of 5 Old 07-14-2017, 10:58 PM
Uniblurb
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2004 WJ 
 
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Make sure all your grounds are good/clean, particularly the PCM ground on one of the coil bracket studs. It's easiest to get to from underneath.

Read through the real good dirty dozen thread in my signature and it shows a photo of the PCM ground in the "grounds" section. Also some good info on cleaning the PCM connector and making sure the receptacles for the pins are tight.

We've seen lots of problems with aftermarket crank sensors if that's what you installed. There's a crank sensor resistance test in my signature from the FSM you may want to try. While pricey the Mopar crank sensor is worth it.

Believe it was ZeeJay, who wrote the dirty dozen, who found the harness side of his coil connector bad. Something you might want to check and good luck.

2004 4.7L WJ Limited, 96 4.0 ZJ


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4.0 , grand cherokee , jeep , misfire

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