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Car misfires

Discussion in '348/355' started by Dice996C4S, Oct 5, 2007.

  1. Dice996C4S

    Dice996C4S Karting

    May 7, 2006
    147
    Cerritos, CA
    Hey guys.. I just noticed that the car misfires a lot especially when idling... On launch from a complete stop, feels like car boggles down a bit then goes... If I have a 25% leak on valve # 2, would this cause the misfire ? Your help will be appreciated.
     
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  3. No Doubt

    No Doubt Six Time F1 World Champ
    Consultant

    May 21, 2005
    66,267
    Vegas+Alabama
    Full Name:
    Mr. Sideways
    Misfires are tough to diagnose (especially over the internet), but one quick test is to disconnect the spark plug wire to your #2 cylinder and let the motor idle. If that cures your idle misfire (ignore that the engine runs rough due to the plug being disconnected momentarily) then you've identified the area of the misfire.

    Obviously you can slowly repeat this test one by one for other cylinders. Wear thick gloves when handling high voltage live wires, by the way.

    If the backfire is still present no matter which of your 8 cylinders is de-sparked at the time, then the problem could be fuel mixture or outside air entering into the exhaust, among other things.
     
  4. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    17,188
    USA
    Full Name:
    Hugh G. Rection
    You will likely need to inspect your spark plugs and spark plug wires. It is common for the one or more wires to short to ground. It is really hot in the valve cover that they run in, and they are packed (more like squished) into a tight space inside. If you have the originals, it would not be a bad idea to just go ahead and replace them preventively. But it would be better to diagnose your problem first.

    Nice wire sets are available from www.kingsborne.com they use the same factory oem brand Beru connectors on each end. Just make sure you specify that they make your set with stock 7mm wire. They made mine with 8mm and it was a really tight fit inside the cam cover.
     
  5. Dice996C4S

    Dice996C4S Karting

    May 7, 2006
    147
    Cerritos, CA
    I'm suspecting that it might be the fuel/air mixture. The fumes on the exhaust is intoxicating to my eyes.. It makes me tear.. The smeel is too strong too...
     
  6. Dice996C4S

    Dice996C4S Karting

    May 7, 2006
    147
    Cerritos, CA
    Or maybe, gas is not being burned properly as my rpm is low when I launch that's causing the car to bog down... On a side note, what RPMs do you launch from a complete stop ? I do about 3000.
     
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  8. F355 SCOTLAND

    F355 SCOTLAND Karting

    Apr 20, 2006
    124
    glasgow
    Full Name:
    mark reilly
    i had a misfiring problem, took all the plugs out and replaced them, still misfiring so called the ferrari dealer in edinburgh scotland and booked it in, they called to say it was the ht leads that were needing replaced and wanted £1,100.00 ($2,000) to supply them, so i sourced a set from a company in london called verdi and they cost me £200.00(much better), as soon as they were fitted it cured the misfire...........
     
  9. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    17,188
    USA
    Full Name:
    Hugh G. Rection
    Well, a "miss" caused by poor ignition will cause the fumes you are describing...I would check your plugs and wires. Most likely the wires though, especially if you still have the original ones from when the car was built. BTW, the Kingsborne wires I mentioned look factory, using the same factory Beru parts, yet cost about 1/3 the cost of oem Ferrari ones.
     

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