Intermittent firing on both banks. Mondial QV 84 | FerrariChat
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Intermittent firing on both banks. Mondial QV 84

Discussion in 'Mondial' started by RichardAguinsky, Jul 17, 2008.

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  1. RichardAguinsky

    RichardAguinsky Formula Junior

    Nov 12, 2007
    478
    Palo Alto, Californi
    Full Name:
    Richard Aguinsky
    #1 RichardAguinsky, Jul 17, 2008
    Mondial QV, 1984, US version. Stock.

    Some time ago, I noticed that when I accelerated the car, I could sometimes hear that sometimes the engine would not fire consistently. Something intermittent.

    I haven't driven the car for almost 3 weeks and today it was quite apparent that something is misfiring. No noticeable loss of power, no hesitation, no sputtering, just that the engine would not fire 100% of the time.

    At first I though it was one of the banks,from searching posts. But when I connected the strobe light to both ignition coils to identify which, they are both intermittent.

    If I accelerate the engine, I can see that the high voltage is not consistent, same in the front and rear. It flashes and misses about 5% to 30% of the time. E.g. I can see the high voltage flashing consistently, then it would go away for a slip of a second, then start flashing again. I tighten all the plugs I could get to.

    Where should I start looking next? Any special place that gets corrorded? Loose connection? Fuse box?

    Any clues, hints, are greatly appreciated.

    Thanks in advance.
     
  2. RichardAguinsky

    RichardAguinsky Formula Junior

    Nov 12, 2007
    478
    Palo Alto, Californi
    Full Name:
    Richard Aguinsky
    #2 RichardAguinsky, Jul 18, 2008
    ??
     
  3. Birdman

    Birdman F1 Veteran

    Jun 20, 2003
    6,689
    North shore, MA
    Full Name:
    THE Birdman
    #3 Birdman, Jul 18, 2008
    If you are sure that this is common to both banks, that rules out a lot of stuff. I would start by checking the crank sensor which is common to both ignition ECUs, and yes, the power to the ECUs which I believe come from the same fuse on the fusebox. Also check the grounds to the ECUs which may be common. If it is on both banks for sure, that doesn't leave too many things to check.

    '84 is a lambda CIS I think, which means there is some ignition stuff that I'm not familiar with though...my knowledge stops at '83! Where is Steve M?

    Birdman
     
  4. barcheta

    barcheta F1 Rookie

    Nov 15, 2003
    3,738
    Maryland
    Full Name:
    Jim
    #4 barcheta, Jul 18, 2008
    have you check to see if the distributor caps are cracked? Also look at the plug extenders and the rotors. While you're at it might as well check the condition of the seals at the distributors. When a crank sensor acts up it's usually cutting out an entire back. you'd notice it as more than an intermittant miss.
     
  5. RichardAguinsky

    RichardAguinsky Formula Junior

    Nov 12, 2007
    478
    Palo Alto, Californi
    Full Name:
    Richard Aguinsky
    #5 RichardAguinsky, Jul 20, 2008
    Hi Birdman,

    I reviewed the schematics you sent me and the ignition is different on the 84.

    I pulled the Lambda out, sprayed all the contacts. Took out all the fuses, relays, sprayed them.

    It is very possible that it is a bad contact somewhere. The car is from Southern California and I see rust on it. Not rain rust, but ocean rust. Quite possible it was on a beach front house for a while.

    This will be a long and painful hunt. I am now following the 328 Miss thread..

    http://ferrarichat.com/forum/showthread.php?t=204999

    Though they are not having much luck either. I already did all that.


    The CIS has only one crank sensor? I'll follow those threads.



    Thanks for your reply!!!!
     
  6. f308jack

    f308jack F1 Rookie

    Jun 7, 2007
    4,300
    Cape Town, South Afr
    Full Name:
    Jack Verschuur
    #6 f308jack, Jul 21, 2008
    In my experience (with cheap strobe-lights) they are always somewhat intermittent.

    If the fault only appears at accelleration, I would rather think the fuel supply is the culprit, maybe a bad Lambda sonde? I am sure that there are test date floating around for these, or swap a known good one in.

    Another possibility is that the ignition doesn't receive the right info regarding your manifold pressure and your advance curve is therefor off. I haven't looked at my ignition at all, so may be off here, but let me not jinx it:)
     

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