Cylinder 7 misfire detected

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Thread: Cylinder 7 misfire detected

  1. #1
    Junior Member dogger's Avatar
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    Default Cylinder 7 misfire detected

    My Tundra started running rough today, and the "check engine" light came on.
    I plugged in my scanner and it came back with P0307 which is a #7 cylinder
    misfire detected. I had a similar situation about 9 mos ago and it turned
    out to be a bad coil pack on cylinder 5. I replaced the coil pack and the
    problem went away that time.

    This time - not so much. I pulled the coil pack from cylinder 7 and replaced
    it with one off the wife's Sequoia. No improvement and same code. I pulled
    the spark plug and it was dark brown and looked like it was just along for the
    ride. I pulled a plug out of the Sequoia and installed it along with the coil
    pack and still no improvement and same code. I pulled all of the plugs and
    found all of them very dark brown with gaps about .045 or more. I installed
    these plugs 25000 miles ago and each one was gapped to .031. The plugs
    are NGK BKR7EVX-11s. I know the "tune" on the supercharger ECU is very
    rich which explains the plug color, but the big gap has me confused. I
    re-gapped all the plugs back to .031 and installed them with all the coil
    packs from the Sequoia, no improvement and same code. I plan to
    replace the NGKs with E3-64s since they appear to have such a short
    service life.

    I think I have covered the electrical end of the diagnostic, so I'm thinking
    possible bad fuel injector? Maybe even a CAT related problem. This is a
    Three catter Cali truck.

    Truck has 55000 miles and gets a bottle of injector cleaner every third
    tank full.

    Any help/suggestions would be greatly appreciated.

    Thanks.

    dogger

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    Default Re: Cylinder 7 misfire detected

    Bad gas? Octane too low? Intake valve carbon build-up? Lazy O2 sensors? How often do you change the PCV valve? Is the air filter clean/new? How is the compression?

    Have you monitored engine performance with a scanner yet? Did it reveal anything unusual?

  4. #3
    Junior Member dogger's Avatar
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    Thread Starter

    Default Re: Cylinder 7 misfire detected

    Bad gas? Octane too low? Intake valve carbon build-up? Lazy O2 sensors? How often do you change the PCV valve? Is the air filter clean/new? How is the compression?

    Have you monitored engine performance with a scanner yet? Did it reveal anything unusual?
    Thanks for the suggestions.

    Gas is good name brand 93 octane from a station with high turnover. PCV replaced every 12 months. Air filter is a TRD reusable, last cleaned and oiled 2 months ago. Compression is good
    and consistent among all cylinders. I ran the scanner with the Truck idleing and didn't get any unusual readings on the freeze frame. I think I have some weak and/or non functioning coil
    packs caused by the oversized gap on these plugs which worked the coils too hard and now they are failing. I just ordered eight new ones that I plan to swap in with new plugs.

    Fuel injectors are all in limits and the Cats are good.

    I'll post the results when i get the coils and plugs installed.

    dogger

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