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Old 01-02-2016, 04:07 PM
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Cylinder #8 misfire on 4.7

Hi Fellow Jeepers! I'm new to this forum and trying to get some answers.
Got P0308 code the other week. I've cganged coils and plugs. No help there, did compression test lasst night. Good compression in all cylinders, with the lowest being 167psi and the highest being 180psi. Jeep still runs like crap. While doing compression test on #8, sounded like it was backfiring through intake.....What could this be? Any help would be great

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Old 01-02-2016, 09:58 PM
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Re: Cylinder #8 misfire on 4.7

Welcome to the garage.
How did this problem started, just out of the blue sky?
What do you mean with back-firing while doing the compression test?
You swapped the ignition parts, but not the fuel injector. You can measure the resistance first, which should be approx 14 ohm (compare it to the others), or just swap its position and see if the misfire follows.
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Old 01-02-2016, 10:10 PM
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Re: Cylinder #8 misfire on 4.7

It started on xmas eve. I went shopping earlier that day and all was good. Later that night went to families house. Started and was runnning rough. CEL was on. Next day, started and CEL was on and ran rough. Took it down road for drive, had no power. When I stepped on it CEL started blinking, turn around and pulled in my shop. Put scanner on it and it showed that code. So I figured coil or bad plug. Replaced all the plugs and coil, even swapped coils around. Still runs like crap. It was making like a back firing noise through the intake while doing compression test on #8. I thought it was odd also. There for I'm here now. I'll have to do the injectors, that's one thing I didn't try. Thank you
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Old 01-03-2016, 03:51 PM
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Re: Cylinder #8 misfire on 4.7

Checked injectors, they tested good. Going to do a chemical block test on coolant. Cheap and quick test. I want to see if gases are getting in to the coolant.
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Old 01-03-2016, 07:01 PM
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Re: Cylinder #8 misfire on 4.7

Eventhough checking the resistance of the injectors is a good first step, i would also swap the #8 with #2, or #4 or #6. A clogged injector still can have the right electrical resistance.
Did you see anything special to the #8 plug? (compared to the others)
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Old 01-03-2016, 09:01 PM
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Re: Cylinder #8 misfire on 4.7

No still looked the same as the others
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