Cylinders 5, 6, 7 misfire

Discussion in 'V8 Discussion' started by tscare, Aug 8, 2018.

  1. tscare

    tscare New Member

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    This happened all of a sudden but getting the codes for misfire on these 3 cylinders. I have extra coils, have switched them out with the extras and between cylinders but its always these 3 cylinders. What is really confusing to me is that on start up, it runs very smoothly for 16 seconds and then starts to run rough and engine light starts flashing. It doesn't matter if I erase the codes or leave them, I turn it off and restart it and the engine runs smooth like it should and after 16 seconds starts running rough. Almost like the PCM is putting the engine in a limp mode or something, but I haven't been able to find anything along those lines. The only thing I've seen that makes any sense is that the knock sensor for the front head is faulty and causing it to misfire? The camshafts are welded. It has run and still starts like a new car until a week ago and now it's like the PCM is causing the front head to misfire? Any help would be appreciated.
     
  2. tscare

    tscare New Member

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    Sorry, 1996 SHO.
     
  3. SHOdded

    SHOdded SHO Member

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    What is the maintenance history on this SHO? What codes are showing up? Cams welded? Mileage?
     
  4. GEN 3 SHO FAN

    GEN 3 SHO FAN SHO Member

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    If engine light is flashing, it's indicating that at least one coil is closed by ECM or isn't fonctionning.

    5, 6, 7 coil are on the front bank, check if you have oil in spark plug well. It can also be your coil #8 creating some kind of short cut.

    I also rode many year ago (V8SHO.com), that on the front main wiring, a bolt into the side support (with the color of the vanity cover on it) had created wear under the wiring enought to create gremlins on the ignition.

    Keep us informed,
     
    SHOdded likes this.
  5. tscare

    tscare New Member

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    Thanks for the info. The car has been well maintained, 70,000 miles, camshafts are welded. The codes that come up are P0305, 306 and 307. No oil in the spark plug wells. Going to look a few things now and will check the wiring under the vanity wire cover. I did switch the #8 coil with the #6 with no change.
     
  6. tscare

    tscare New Member

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    FIXED!!! Who would've thunk it, but I have a 97 donor sho and thought I would just swap sensors to rule things out. The first one being the easiest was the MAF housing which has the MAF sensor and Intake air temp sensor. Shazam, no more misfires. I swapped just the IAT sensor back, no misfires. Put the original IAT and MAF sensors back in and no misfires. So I'm guessing it was just a loose connecter and needed a little wiggle. I feel so lucky I'm going out to get a lottery ticket!
     
    Josh Jackson and SHOdded like this.
  7. SHOdded

    SHOdded SHO Member

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    Gotta love a simple fix :D
     
    stephen newberg likes this.

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