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  #1  
Old May 16th, 2018, 22:04
socalrex1 socalrex1 is offline
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Misfire help needed

I have a 2001 Cherokee sport with the 4.0 4x4 and it has a random misfire causing it to run like absolute shit.
Process of elimination has begun and I have no clue what it could be at this point. So to start Iíll list everything I have tried and see if anyone has suggestions

1. Compression tested all between145-155
2. Fuel pressure checked consistent at 50-55 driving or idling
3. New plugs
4. New coil pack
5. New crank sensor
6. New cam sensor and synchronizer
7. New map sensor
8. New pcm ( flashed correctly)
9. New engine harness(replaced yesterday off same exact vehicle)
10. New o2 sensors (all4)

I have been trying to figure this out for quite some time and am getting to my wits end any advice would be greatly appreciated
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  #2  
Old May 17th, 2018, 05:02
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Tim_MN Tim_MN is offline
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Re: Misfire help needed

Are all the new engine sensors genuine Jeep parts ?

Read this >> http://jeep.blackonyx.net/pdfs/jcss.pdf , and then grab a toothpick. If necessary, print it out and find a shop that understands the info and has a DRB-III scan tool and oscilloscope.
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Old May 17th, 2018, 05:24
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old_man old_man is offline
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Re: Misfire help needed

First run a can of BG44 through the gas. It will clean the injectors and carbon out.

I run a can every 10k miles in everything I own.
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Old May 17th, 2018, 06:49
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RNMedic RNMedic is offline
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Re: Misfire help needed

subbed, I have a similar prob thought it was heat soak, got the insulators from Jeep. was ok. Now its warm again its doing it again. Checked all the above, did seafoam, moved injectors. The injector code always sets before the misfire. Wiring all checks out ok. Starting to suspect PCM.
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Old May 17th, 2018, 10:41
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Tim_MN Tim_MN is offline
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Re: Misfire help needed

PCM failure is highly unlikely and only should be considered after a complete and thorough diagnostic of the more common and likely causes of misfires.
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  #6  
Old May 17th, 2018, 10:49
RCP Phx RCP Phx is offline
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Re: Misfire help needed

That's what happened to my 2k, bad wire shorted out my PCM output on #6!
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Old May 17th, 2018, 17:33
socalrex1 socalrex1 is offline
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Re: Misfire help needed

Quote:
Originally Posted by Tim_MN View Post
Are all the new engine sensors genuine Jeep parts ?

Read this >> http://jeep.blackonyx.net/pdfs/jcss.pdf , and then grab a toothpick. If necessary, print it out and find a shop that understands the info and has a DRB-III scan tool and oscilloscope.

I have already tried the toothpick and ended up just replacing the whole synchronizer after that didnít fix it. I unfortunately donít have the means to get it into a shop for them to scan it.
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Old May 18th, 2018, 05:59
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90xj06 90xj06 is offline
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Re: Misfire help needed

are you getting any codes other than a misfire? is it constant or intermittent?
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