Help Troubleshoot Misfire?
02-12-2018, 05:48 AM
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Help Troubleshoot Misfire?
2001 Cherokee XJ @ 137K miles. A few days ago the check engine light came on and started flashing.. got the codes read and here's what I have:
- P0300 multiple cylinder misfire
- P0305 cylinder #5 misfire
- P0306 cylinder #6 misfire
- P0455 evap emission system leak (pending code)
The Jeep has a hard time starting and unless I keep the rpms at about 1500/2000, it'll shut off. Once it's warmed up, it idles and drives extremely rough and lacks power at higher speeds (above 45mph). I replaced the spark plugs with copper NGKs and tested the primary and secondary resistance of the coil pack and it's the same resistance as a brand new one (tested it in store). Placed a spark plug in each coil pack boot and it fired from all 6 boots. What should my next steps be? Maybe fuel injectors but what are the odds of both 5 and 6 going bad at the same time? Could it be the O2 sensor? Any help would be appreciated.
- P0300 multiple cylinder misfire
- P0305 cylinder #5 misfire
- P0306 cylinder #6 misfire
- P0455 evap emission system leak (pending code)
The Jeep has a hard time starting and unless I keep the rpms at about 1500/2000, it'll shut off. Once it's warmed up, it idles and drives extremely rough and lacks power at higher speeds (above 45mph). I replaced the spark plugs with copper NGKs and tested the primary and secondary resistance of the coil pack and it's the same resistance as a brand new one (tested it in store). Placed a spark plug in each coil pack boot and it fired from all 6 boots. What should my next steps be? Maybe fuel injectors but what are the odds of both 5 and 6 going bad at the same time? Could it be the O2 sensor? Any help would be appreciated.
02-12-2018, 04:21 PM
#2
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Year: 1987
Model: Cherokee (XJ)
Compression check would be your next step.
How does your oil look? Like a milkshake or normal? Not sure if you know but the 00-01 XJs are known to have a head that cracks over time.
How does your oil look? Like a milkshake or normal? Not sure if you know but the 00-01 XJs are known to have a head that cracks over time.
02-12-2018, 04:40 PM
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Year: 2000
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One thing I think I have learned from my '00 is that misfire codes can be just cause the Jeep is throwing a little hissy fit. Example. I swap out my anti-freeze every 2 years. Before I bought the Lisle funnel, awesome by the way, I would fill it up as much as I could. Drive it around, keeping an eye on the levels as the air burped out, and in less then a week would be good to go. Anyway the first time I drove it to start the process I got a misfire CEL. My little theory is that an air pocket hit the temp sensor in the thermostat housing and threw the CEL. When it cooled added some more anti-freeze, cleared the code, and that was that. My point is if this were me I would see what is up with the P0455 first. If you can fix that then I would clear all the codes, drive it, and see what happens. I run the heat shield and cheapo Champions. One thing I don't have problems with, yet, are heat soak and misfires. And mine is a CA emissions one.
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