Mondial QV Spits and sputters a little then | FerrariChat

Mondial QV Spits and sputters a little then

Discussion in 'Technical Q&A' started by srephwed, Jul 21, 2018.

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  1. srephwed

    srephwed F1 Veteran
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    #1 srephwed, Jul 21, 2018
    Good day everyone. I am hoping someone has experienced this problem. Three years ago I installed a 3.2 and XDI ignition in my Mondial. Until recently it has run perfectly. It has decided to start spitting and sputtering with the idle dropping 100 rpm. Driving along it will make a single pop or backfire in the intake then run perfect with idle speed increased. Then it will repeat the cycle. I feel it has to be electrical because of the pop in the intake but I don't know where to start Thanks for any help
     
  2. miketuason

    miketuason F1 World Champ
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    #2 miketuason, Jul 27, 2018
    I had similar symptoms on my 84 QV and turned out that one of my Digiplex box was went bad.
     
  3. srephwed

    srephwed F1 Veteran
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    #3 srephwed, Jul 27, 2018
    Thanks for the input but my XDI eliminates the digiplex. Just seems to be ignition because one pop or back fire and it runs perfect. I have invested in new injectors. Maybe they are clogging as they run and the pop or back fire is like back flushing the toilet then it clogs again after time. 6 years ago when I took delivery of this car the injectors were the issue. I will let you know.
     
  4. miketuason

    miketuason F1 World Champ
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    #4 miketuason, Jul 27, 2018
    That was my first thought at first, my injectors are clogging up but then I remember I just had my injector ultrasound cleaned five years ago. My car would backfire, spit, cough, misfire a lot on both high RPM and low RPM that it wouldn’t idle for long as it will die. Now since I had a pair of the Euro Digiplex that I’ve been keeping for many years, I tried switching them and right away my car ran like a normal car, actually better since the Euro Digiplex has better timing curve. So, I’m just saying your problem could be the same or maybe you’re right, it could be just your injectors.
     
  5. srephwed

    srephwed F1 Veteran
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    #5 srephwed, Jul 30, 2018
    Replaced injectors. Sadly no improvement. XDI is supposed to be hard on plug wires. Have new ones comming
     
  6. Andy 355

    Andy 355 Formula Junior

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    #6 Andy 355, Jul 31, 2018
    Sounds more like a lean fuel system condition. There are many things that can cause this. This car is fitted with cis fuel injection?
     
  7. srephwed

    srephwed F1 Veteran
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    #7 srephwed, Aug 4, 2018
    happy days. The plunger for the flap in the intake was not operating freely. I suppose the single pop would blow it back in place and run ok for a while. Nice to have my car back
     
  8. Andy 355

    Andy 355 Formula Junior

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    #8 Andy 355, Aug 5, 2018
    This is common on cis. Also make sure the roller that pushes on the metering head pin is free to spin.
     
  9. mike32

    mike32 F1 Veteran

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    #9 mike32, Aug 22, 2018
    Have you noticed any increase in the engine oil level or a misfire from the engine ? If the diaphragm in the metering head has a hole or is split it will overfuel a particular cylinder and go past the piston into the sump, engine runs rough etc. Repair kits are cheap on e bay and an easy fit
     

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