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Backfire

Discussion in '348/355' started by tommywcom, Jun 29, 2015.

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  1. tommywcom

    tommywcom Rookie

    Oct 17, 2010
    34
    Vancouver, Canada
    Full Name:
    Tom
    #1 tommywcom, Jun 29, 2015
    This happened to me this morning for the first time in the 5 years that I have owned my 348TS. In fact, I have not experienced in any cars, period.

    We have a 3-lane bridge in town - the middle lane changes to either direction depending on the time of day. I was in that middle lane while it was about to change - you get a green lane light changing to yellow then red.

    All the cars were moving over to the correct lane. I stayed in the middle and there was a very new Maserati right behind me. So we were kind of egging each other on. I stepped on it, and stayed in the middle lane for a couple more minutes.

    When I finally pulled over to the correct lane (and so did the Maserati), I let go of the throttle to merge into a gap. That's when it happened - right after I slotted in there. It was huge BOOM sound. And I'm pretty sure it was from my car as I could kind of feel it too.

    I didn't see any fluid leaking or any abnormality after that. Just kept driving.

    Oil temperature at the time was probably a little past halfway between cold and proper temperature.

    Looking it up online, it seems like backfire happens when the air-fuel mixture is overly lean, which tends to happen when one lifts off the throttle. Makes sense.

    Has this happened to anybody?
     
  2. SoCal1

    SoCal1 F1 Veteran
    Owner Silver Subscribed

    Jun 14, 2011
    8,633
    SoCal LA/OC/New Mexico
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    Tim Dee
    #2 SoCal1, Jun 29, 2015
    Off throttle is most likely accumulated unburned fuel in the muffler igniting from heat or exhaust leak

    Check your plugs and see if one is running rich, leaky injector ect. Check for exhaust leaks. If good keep an eye on it

    Most likely the car just needed to fart

    :)
     
  3. AceMaster

    AceMaster Three Time F1 World Champ

    Feb 6, 2009
    34,778
    Ontario, Canada
    Full Name:
    Mike
    #3 AceMaster, Jun 29, 2015
    This is common with straight pipes I believe.
     
  4. tommywcom

    tommywcom Rookie

    Oct 17, 2010
    34
    Vancouver, Canada
    Full Name:
    Tom
    #4 tommywcom, Jun 29, 2015
    My car has no catalytic converter but does have 2 mufflers (one on top of another) ...
     
  5. AceMaster

    AceMaster Three Time F1 World Champ

    Feb 6, 2009
    34,778
    Ontario, Canada
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    Mike
    #5 AceMaster, Jun 29, 2015
    Sorry that's what I meant. I had a car with just mufflers, no cats, and I would get backfires regularly.
     
  6. ///Mike

    ///Mike F1 Veteran

    Dec 11, 2003
    6,097
    Bugtussle
    #6 ///Mike, Jun 29, 2015
    As Tim said, backfiring through the exhaust is indicative of unburned fuel in the exhaust sytem, either due to an ignition fault or excessive fuel being injected into the engine. If the car runs smoothly otherwise, a leaky injector could very well be to blame.

    "Backfiring", (or spitting back) through the intake usually indicates a lean condition, which does not sound to be the case here.
     
  7. zc911

    zc911 Formula Junior

    Mar 4, 2014
    707
    Brampton, Ontario
    Full Name:
    Rob
    #7 zc911, Jun 29, 2015
    Mine did the same and at least one of the fuel pressure regulators was bad. It was just pushing fuel right up the vaccume hose and into the intake
    It was also hard to start when hot
     
  8. vvassallo

    vvassallo F1 Veteran

    Aug 4, 2006
    8,329
    Palos Verdes
    Full Name:
    Vince V
    #8 vvassallo, Jun 30, 2015
    I will get a slight backfire only in 2nd gear and only if I rev it up and suddenly lay off the throttle in a slow down condition. Won't happen if the car is at rest. I figure it's unburned fuel in the cat or muffler generated at low speeds but wide open throttle that ignites. My injectors are new, but my induction and exhaust system is modified for high flow at WOT.
     
  9. vracer

    vracer Formula 3

    Jun 23, 2014
    1,098
    NorCal
    Full Name:
    Richard
    #9 vracer, Jul 1, 2015
    Most "backfires" are actually "afterfires" as Tim suggested above.
     
  10. Enzojr

    Enzojr F1 World Champ

    Dec 12, 2013
    14,001
    West of PDX
    Full Name:
    Tomy
    #10 Enzojr, Jul 1, 2015
    That's your F car letting the Mas know in Italian second place is not a win ;)
     

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