Misfire - Ignition Advice

Electrical and Ignition

  1. Pana.Mopar

    Pana.Mopar Duster Down Under

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    Hi All, Hope everyone is staying safe.

    Just want to ask advice with misfire/ignition on my 383. It's misfiring slightly above 2000rpm and damn annoying. It has stock Mopar electronic dizzy and MSD Streefire Ignition module. Have change plugs, leads and still hasnt fixed it. Any ideas on where I should look into it?
     
  2. Bewy

    Bewy Well-Known Member

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    Pana,
    I am in Sydney. PM me a ph # & I will give you a ring.
     
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    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      Describe more about the problem. Is this at any throttle, or not there under light cruise but there under heavy throttle, etc?

      Did this pop up all by itself and had been running well, or did you change something and "now it's there?"
       
    • Pana.Mopar

      Pana.Mopar Duster Down Under

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      It's been there for ages. Its usually once the car is hot and above 1,500rpm on the throttle. Doesn't do it at low speed or cruise.
       
    • Early a body

      Early a body Well-Known Member

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      I would need to know what carb you are running. What is your ignition timing at idle at all in?.

      i would check the reluctor in the distributor, I had a similar problem a few years ago on a older mp distributor, turns out the reluctor in the distributor looked like a mouse was chewing on it so where it passes the pick up it was not straight any more it was literally all chewed up. Once I replace the reluctor problem solved.

      But your carb jetting/ adjusting and what timing you are at make a difference too if the reluctor is in good shape. Is the carb sitting on the intake or is there a spacer etc.
       
    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      So you are saying that heavier throttle causes it? I would suspect low spark voltage. Bad coil wire, bad coil, something wrong in the ignition module, or LOW 12V SUPPLY VOLTAGE to the unit, caused by a number of things, including mis-wired (are you using a ballast and is it supposed to?) or other harness problems

      Try separating the ignition system from the harness and 'hot wire' it direct and see if that makes a difference
       
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      • Righty Tighty

        Righty Tighty FABO Gold Member FABO Gold Member

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        Would using an incorrect ballast resistor (4-prong instead of 2-prong) cause this?
         
      • 67Dart273

        67Dart273 FABO Gold Member FABO Gold Member

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        Sure
         
      • bee1971

        bee1971 Active Member

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        Wouldn’t a MSD Streetfire Module require full 12v directly from the Battery

        And then the coil + is directly fed off the MSD Module

        Why would anyone run a Ballast Resistor with that system , when it should bee completely eliminated within the wiring schematic
         
        Last edited: Jun 28, 2021
      • Righty Tighty

        Righty Tighty FABO Gold Member FABO Gold Member

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        I was more asking for my own knowledge as opposed to troubleshooting this particular situation, sorry.
         
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        • Pana.Mopar

          Pana.Mopar Duster Down Under

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          I'm running Quickfuel 750 Double Pumper on it. Ignition timing is at 14 (I think?) Yeah I've got an old MP distributor on it.
           
        • Pana.Mopar

          Pana.Mopar Duster Down Under

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          Correct, there's no Ballast Resistor on this.
           
        • Pana.Mopar

          Pana.Mopar Duster Down Under

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          Yeah, when the car is hot it happens thru the mid rev range. Also noticed that when I jump on the throttle ant high revs it wants to die (sounds like a fuel issue)

          Have changed all the leads on it. MSD Blaster Coil is near new. There's no ballast resistor on this set up.
           
        • fishmens67

          fishmens67 FABO Gold Member FABO Gold Member

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          sounds like you're running the factory Mopar performance curve . are you hooked to vacuum advance?
           
        • Pana.Mopar

          Pana.Mopar Duster Down Under

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          Nah, vacuum advance is blocked off.
           
        • fishmens67

          fishmens67 FABO Gold Member FABO Gold Member

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          If I remember your combo right you should be running initial timing of at least 20 probably 22-24 with 36-38 total.
          I'd start there and retune the carburetor and check fuel flow when it's hot.
           
        • Pana.Mopar

          Pana.Mopar Duster Down Under

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          Yeah, I think I'll go back and do timing and carby and see how it goes.
           
        • bee1971

          bee1971 Active Member

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          Old Mopar Distributor

          Bushings

          Distributor cap/rotor

          Rotor Phasing

          Did you check the gap on your reluctor / pickup coil ? .008 with a brass feeler gauge
          Check it at all eight points on the reluctor , see if the pickup coil is hitting the reluctor while spinning

          Could bee the pickup coil itself failing also when hot

          If you think it’s the MSD Streetfire Ignition Module failing , how hard would it be to reinstall the Mopar/Chrysler ECU or Ignition Module on the firewall , or even a points distributor
           
        • Pana.Mopar

          Pana.Mopar Duster Down Under

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          Thanks mate. Will check these things. I've left all the original electronic wiring there so wouldnt be hard to put a new dizzy and original dstyle ECU back in.
           
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