#4cylinder miss firing

Discussion in '1997 - 2003 Ford F150 Truck Forum' started by WillFord, Feb 27, 2020.

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  1. WillFord

    Hello I have a 99 Ford Expedition the number 4 cylinder is misfiring I switched the plug wire/coil pack with the number 3 cylinder, it ran great for 3 days. Then switched the plug wiring with another cylinder and it ran great for one day. Still same thing, what is the next possible thing I should look for next?
     
    WillFord, Feb 27, 2020
    #1
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  2. FTZ HAIC Staff Member Oregon Chapter Founding Member

    Have you pulled the plug from the cylinder to look for signs of oil fouling?
     
    FTZ HAIC, Feb 27, 2020
    #2

  3. WillFord

    Yes, I just installed new plugs 3 wks ago. I mentioned in my first post that I switched the plug wires/coil pack w/ another cylinder. It was just the wires. Today I swapped the 2 coil packs. Ran great for 500 ft. Then back to misfiring. Don't know if different cylinder misfiring, scanner hasn't found yet. Will check again tomorrow after I drive it around some.
     
    WillFord, Feb 28, 2020
    #3

  4. WillFord

    Well, drove to work and back, still misfiring yet once in a while it would run good but only for a minute or two . Scanner shows no codes found???
     
    WillFord, Feb 28, 2020
    #4

  5. FTZ HAIC Staff Member Oregon Chapter Founding Member

    The scanner won't show a code until it becomes a "hard code", where enough misfires have happened. The high-end scanners like dealer techs use will show pending codes, number of misfires, etc. If you can get ahold of a good scanner that shows cylinder contribution data it will show if it's a lean misfire.

    Check the injector plug at the cylinder to make sure it's seated properly (I would suspect this first). Odds are it's a lean misfire from that being loose, the wiring having issues or dirty injector.

    Lean misfires could also be happening if the MAF is dirty. The rear cylinders (4 and 8) tend to show this first. Also check the well for any signs of water.

    The reason I asked about oil on the plug is not that you changed the plugs, but because reading the old plug will tell you more about this than anything. The plug will tell you if it's lean, oil fouling, rich, etc. There are charts online in google image search that shows what each looks like.
     
    FTZ HAIC, Mar 2, 2020
    #5

  6. WillFord

    Thank you so much for your response's on this. I do remember when I pulled that plug out there was no oil or show any signs of fouling. The plug itself was in pretty good shape. I went ahead and replace the coil packs yesterday even though I probably didn't need them, but I will check out everything you suggested and we'll go from there thank you very much
     
    WillFord, Mar 2, 2020
    #6
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