1. #1
    grooveman's Avatar
    grooveman is offline Member
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    Cylinder Misfire?

    Fired up the Jeep this morning and it sounded like it was running on 5 cylinders. Pulled codes P0306 (Cylinder 6 misfire detected) and P0155 (O2 sensor heater malfunction (Bank2 Sensor1). I live in a cold climate and let the gas get low. Added some gas line antifreeze and let it run a while but its still running rough. I plan to start tearing into it when it warms up enough, just wanted to get ideas on what I should check first. Its a 2003 TJ, 4.0L.

    Thanks!

  2. #2
    Saddle Tramp's Avatar
    Saddle Tramp is offline Senior Member
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    Re: Cylinder Misfire?

    Shot in the dark here- Are 03s coil over plug? If so I would start there.

  3. #3
    SteelHeadz's Avatar
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    Re: Cylinder Misfire?

    Yes Kriss, it's a Coil rail system..

    Grooveman, i would check the wiring at the end of the coil rail at the connector and where it routes across the rear of the cylinder head. Sometimes the wiring will chaffe on the engine block and create a short or a misfire in this case. The P0155 indicates a bad sensor all in all if the connector is good. Bank 2 meaning , the rear exaust pipe from the manifold and the top sensor which is sensor 1(Upstream O2 sensor).
    Confucious says: Don't eat the snow where the huskies go!

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    grooveman's Avatar
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    Re: Cylinder Misfire?

    Yes Kriss, it's a Coil rail system..

    Grooveman, i would check the wiring at the end of the coil rail at the connector and where it routes across the rear of the cylinder head. Sometimes the wiring will chaffe on the engine block and create a short or a misfire in this case. The P0155 indicates a bad sensor all in all if the connector is good. Bank 2 meaning , the rear exaust pipe from the manifold and the top sensor which is sensor 1(Upstream O2 sensor).
    Ok, as soon as it warms up enough I'll check that.
    BTW, Kerrville close to my hometown. (Uvalde). Wish I was back down there.

    Thanks for the help

  5. #5
    SteelHeadz's Avatar
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    Re: Cylinder Misfire?

    LOL, yep, Uvalde, great place to go for hunting wild pigs. We have them here too but it's getting harder and harder to find ranchers that will let you hunt them off their property..
    Confucious says: Don't eat the snow where the huskies go!

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