Cyl 4 random misfire.

Discussion in 'KJ General Discussion' started by SabaII, Jun 29, 2012.

  1. SabaII

    SabaII Full Access Member

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    Oct 8, 2010
    Rochester, MN
    Alright I am getting annoyed now. 3.7L Auto 4wd. Cyl 4 will misfire when I first start the Jeep, I shut down and re-start and it goes away. Doesn't matter if its already warm or cold. Very intermittent on when it happens. It could do it every time I start up one day or it could happen once in a day and not again. Here is a list of what I have done.

    1. Started with the plugs. Cyl #4 showed no signs of fouling or excess carbon build up or heat. They all were pretty worn.

    2. Thought in my head the worn plug put extra load thus heat in the coil and burned it out. Made sense to me so for $20 I went and got a new coil. Put that on but no dice.

    3. Swapped injectors with #2. Now the tip of the #4 injector had some white build up on it but I figured that was just condensation build up and it wasn't covering any holes. After the swap it ran fine for a couple of weeks and now this morning came back. #4 again.

    Any insight guys? I have come across cars with bad batteries doing some weird things before. I tried searching and came up with head issues with some but no one person had the exact symptoms. Thanks.

  2. lautinjr

    lautinjr Full Access Member

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    Oct 15, 2011
    Las Vegas
    I had a random misfire forever that I couldn't find. Finally changed the Cam sensor out of curiosity and problem solved. Being yours is specific to #4 doubt that's the problem.