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Ignition problems

Discussion in 'Technical Q&A' started by sunburn, Dec 9, 2003.

  1. sunburn

    sunburn Formula Junior
    Silver Subscribed

    Nov 2, 2003
    693
    Dawsonville, GA
    Full Name:
    Rick R.
    I just bought a 1995 456 GT and need some assistence in how the ECU triggers the coil packs. The car has developed a missfire (actually no spark at all on cylinders 2 and 5). It was happening when it was cold and then it would go away. Today it continued even once the car was warm. There is no spark for those cylinders directly from the coil pack so I've eliminated any plug wire issues. The system never shows a check engine light but will show a slow down 1-6 light if the car is run for 5 miles or so at 35-45 mph.

    First, does the car have an ECU for each bank of cylinders? I can only find 1 under the drivers side kick panel.

    Second, does the ECU drive the 12V trigger to the coil pack or are there separate ignition amps.

    Third, has anyone heard of a coil pack failure that only effected 2 cylinders?

    Thanks for any insight you can give.
     
  2. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,159
    Texas
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    Steve Magnusson
    Have you read your OM carefully? -- IME often there are good architechtural descriptions given (e.g., 1 or 2 ecu for a particular function).

    Agree that it's a strange problem, but if you've truly got 2 non-firing cylinders in a bank then the warning light is probably doing it's job well and shouldn't be ignored.

    Give us non-456ers a description regarding "coil packs" -- are you distributorless? -- does each bank have its own (swappable?) pack?
     
  3. james patterson

    james patterson Formula Junior
    Professional Ferrari Technician

    Dec 8, 2003
    417
    Dallas Texas
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    James Patterson
    Your problem is most likely the coil pack, it is a wasted spark system with 2/5 sharing the same coil, 3 coil per pack. We have had a number of this style coilpacks fail on 348,512 models. As Mr. Magnusson suggested ,to make sure, swap the coils from bank to bank and see if the problem does not move to the 7/12. Good luck.
     
  4. sunburn

    sunburn Formula Junior
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    Nov 2, 2003
    693
    Dawsonville, GA
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    Rick R.
    Thanks for the input guys. The 456 is without distributor. It does have 2 coil packs, one for each bank so a swap is the next step. The task is not an easy one as the bolts that hold the packs in place were most likely the first pieces to come down the assembly line and the car was built around them.
     
  5. sunburn

    sunburn Formula Junior
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    Nov 2, 2003
    693
    Dawsonville, GA
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    Rick R.
    Good call James! I replaced the coil pack for the 1-6 bank and we're back in business . . . and the great thing is it was under $200 bucks. It seems like I can't even change the air in the tires for under $200 bucks!
    Thanks for the input.
     
  6. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    16,558
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    Hugh G. Rection
    Wow! That is awesome.
     
  7. DGS

    DGS Three Time F1 World Champ
    Rossa Subscribed

    May 27, 2003
    33,566
    MidTN
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    DGS
    No, no, no. The japanese build cars that way.

    On italian cars, you maneuver the bolt (more likely nut) into place by hand (relying on thin dextrous fingers (which make you popular with le ragazze)).

    Then you wrap a strand of al Dente Linguini around the part with the long end routed through the labyrinth to where you can grasp it.

    Go have some wine.

    When you return, the hardened pasta becomes your custom wrench.

    When the pasta shatters and breaks away from the part, it's "tight enough".

    That's why it's so hard to find torque settings for these cars in newton-metres. They're calibrated in percent-litres. (Litres of wine consumed at a given percent relative humidity before tightening.)

    :D
     

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