Diagnosing Misfire code, advice?

Discussion in 'Renegade Stock Tech' started by Murf, Jan 14, 2020.

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  1. Murf

    Murf New Member

    Joined:
    May 10, 2018
    Messages:
    16
    Location:
    Indiana
    I have a 2017 Latitude with 2.4 engine.

    In June 2019 at 50K miles I replaced the spark plugs with "NGK (5018) LFR5AGP" (Platinum plugs).

    In November 2019 while driving on a trip I experience rough engine at 70MPH and then after awhile Service Engine light came on. Went to AutoZone and they pulled a "P0301 Cylinder #1 Misfire" code.
    I pulled the boots off all 4 plugs and added ample amount of dielectric grease (I didn't put much on before). When I started it back up and the Service Engine light and message disappeared all on its own to my amazement. No problems on trip home.

    Everything has been fine until this weekend. While setting in a drive thru I thought I notice the engine did a little rough idle for a brief couple seconds and that was it.
    The next day I went somewhere. When I came back out and started the Jeep the Sevice engine light came on. I pulled the code when I got home and it is the "P0303 Cylinder #3 Misfire" . The engine seems to be running without misfiring as far as I can tell by the feel and sound.

    I now have 62K miles on the Jeep. Can a different plug than the OEM be detected my the "computer"? Is it all that particular about plug brand/type? After all, isn't all that matters is there is a spark.

    I'm trying to think what it could be since it switched cylinders and the plugs is the only thing I can come up with.

    How do I diagnose this. Starting with the simplest things first.

    Thanks for your help,
     
  2. IDoMy0wnRacing

    IDoMy0wnRacing Active Member

    Joined:
    Apr 18, 2019
    Messages:
    397
    Location:
    Pioneer, California
    Dielectric grease. A dab, something the size of a tic-tac is recommended. don't put tooo much.

    Trouble code for the P0303. Swap the coil with the code, cylinder 3 with a coil from a different cylinder, cylinder 2 for example to see if the DTC move to cylinder 2. Drive it around for a while and recheck for codes. If the faults shows up at cylinder 2, the coil is at fault. Replace the coil.
    If the code comes back to cylinder 3, the plug is at fault.

    It sounds like one of your coils is failing. Not uncommon with our 2.4l engines.

    NGK is a very good plug for our 2.4l.
    AVOID Autolight. Autolight has never worked well in Chrysler vehicles.
     
  3. Murf

    Murf New Member

    Joined:
    May 10, 2018
    Messages:
    16
    Location:
    Indiana

    Thanks. Good idea on the coil swap. I had the error on cylinder 1 in November. Now it is on cylinder 3. I only felt it briefly and that was all on Cylinder 3. I got to looking on the internet and found this video:
    I didn't realize all the trouble a bad PCV valve can cause. So I ordered a new one and will see if that helps. I believe I still have the original PCV valve with 62K on it - never been changed.
     
    IDoMy0wnRacing likes this.

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