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328 shutdown cough

Discussion in 'Technical Q&A' started by DGS, Jul 30, 2004.

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  1. DGS

    DGS Seven Time F1 World Champ
    Rossa Subscribed

    May 27, 2003
    73,023
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    DGS
    #1 DGS, Jul 30, 2004
    My 328 has taken to giving a final loud cough after shutting down. Any ideas what causes this? Mixture? Timing? Allergies? ;)
     
  2. Mike328

    Mike328 F1 Rookie

    Oct 19, 2002
    2,655
    Boulder, CO
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    Mike
    #2 Mike328, Jul 30, 2004
    By cough, do you mean 'backfire'? :)

    I believe this can be caused by either a too-rich mixture or by timing.

    Unless you really know what you're doing (I don't), there's not a whole lot you can do on your own...

    In the mean time, to fix the "Symptom" (like if you're in a grocery store parking lot and don't want to scare all the happy shoppers), push the brakes, let the clutch out halfway to drop the RPMs to just barely idling (400 rpm or so), then turn the car off. Not graceful or elegant but will prevent embarassment until you can get the root cause of the issue addressed...


    Good luck,

    --Mike
     
  3. thecarreaper

    thecarreaper F1 World Champ
    Silver Subscribed

    Sep 30, 2003
    18,125
    Savannah
    #3 thecarreaper, Jul 30, 2004
    on a 328 with fuel injection i would say vaccum leaks. timing and rich mixture are also good suggestions, but vaccum leaks will affect a FI car the same way as a carb car. spray around the intakes with quality carb / throttle body cleaner. do this on a stone cold running engine. you will see a sharp change in engine rpms and bubbles where there are any vaccum leaks at the gaskets.
     
  4. jester1

    jester1 Karting

    Jul 24, 2004
    68
    Toronto
    #4 jester1, Jul 30, 2004
    hi
    just for ref sake. If you pop from the intake its usally timming or lean mixture. If it pops through the exhaust its usally running rich.
    p.s. claritine might help:)
     
  5. abarre

    abarre Formula Junior

    Jul 9, 2003
    295
    #5 abarre, Jul 30, 2004
    My 3.2 Mondial does the same thing. When you shut it down, you hear a final "hurumph" in the exhaust system after the engine spins completely down. Definitely not a backfire, kind of like it's clearing its throat. Very deep in tone.
     
  6. DGS

    DGS Seven Time F1 World Champ
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    #6 DGS, Jul 31, 2004
    Thanks for the inputs. Not a full-on backfire, more of a single, throat-clearing cough. Maybe a tiny backfire, but it's nowhere near that loud. Not much louder than the exhaust. Just a single boomp after the engine stops. Kind of like that last tagged on note at the end of the Italian anthem on the podium. ;)

    Vacuum seems to ring a bell, as it might also explain the unstable idle. Alas, there's miles and miles of vacuum plumbing on a CIS machine, including the (suspect) aux air valve, the idle intake pitots, etc, etc, etc. And I'm a bit cramped in my garage for comprehensive diagnostics. (Or ventilation with the engine running.) But it helps to understand where I should be looking.
     
  7. abarthracer

    abarthracer Formula Junior

    Dec 6, 2003
    373
    Falmouth, Cape Cod
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    david S.
    #7 abarthracer, Jul 31, 2004
    My 85 Mondial with the 3.0 does the exact same thing. Havn't been able to figure out why. Guess I need to attack it with a can of carb cleaner to. These cars have the most bizzare idiosyncracies I have ever seen. And this is coming from someone with 1 45yr old German car and 3 30-40yr old Italian oddities!!!! Thanks for making me feel better that I am not alone in noticing the "cough".
    David
     

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