83 QV Idle misfire issue after going hard

Discussion in '308/328' started by FerrariMech1, Mar 12, 2018.

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  1. FerrariMech1

    FerrariMech1 Karting

    Dec 14, 2014
    70
    Dayton, OH
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    Michael Wilson
    I'm going to be candid and say I don't normally run my car up to redline all that often. Once in a while I get saucy and decide to go crazy on back roads to really feel the 308 shoulder into corners and make Italian music for all to hear. 5,000RPM is usually a good number to aim for on my normal drives.

    Lately, I came across an issue that only seems to come out after bringing it up to redline. What will happen is: I'll launch out, slam gears for a few miles and when I come to a stop the car will settle back into its idle, only to "lope" and run rough. It sounds for sure like it's running on all 8, but just sorta uneven and abnormal. Blipping of the throttle does nothing; it takes a shutdown and restart for the idle to return to normal.

    On a normal basis, the car runs perfectly fine. Cold and Warm starts are good, there is balance through the entire RPM range, and the A/F Ratio was verified good before my run today.

    Now, I've had the fuel distributor and CPR rebuilt by Larry Fletcher some years ago and the ignition system has been gone through by me (wires, iridium plugs, cap, rotor, and two of the three flywheel sensors replaced)... the RPM sensor is still original.

    Does anyone have any theories? Ideas?
     
  2. yelcab

    yelcab F1 Veteran
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    Mitchell Le
    We don't even have any idea what year and model this car is, Michael?
     
  3. FerrariMech1

    FerrariMech1 Karting

    Dec 14, 2014
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    #3 FerrariMech1, Mar 13, 2018
    Last edited: Mar 13, 2018
    it’s in the title... 83 Q.V.

    Edit: i guess I should’ve added 308 cause it’s not a Mondial


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  4. FerrariMech1

    FerrariMech1 Karting

    Dec 14, 2014
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  5. Steve Magnusson

    Steve Magnusson F1 World Champ
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    What version '83 QV?

    Do you mean:

    1. I turn off the engine when having the idle problem, and I immediately restart, and the idle is fine,
    or
    2. I turn off the engine when having the idle problem, and let everything cool down to ambient for maybe a few (or more) hours, then at the next restart, the idle is fine?
     
  6. thorn

    thorn Formula 3
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    Given you aren't posting in the mondial forum + your post title + your details page, I assumed it was a '83 308QV.
     
  7. johnk...

    johnk... F1 Veteran
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    Jun 11, 2004
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    Drive the car and enjoy it. Probably nothing to worry about. Not over heating and good oil pressure? Get in a drive. It will let you know if it something needs attention. That's my idea.
     
  8. thorn

    thorn Formula 3
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    I think the car is doing that. ;)

    Hard to do much more than throw out theory at this point, but I'd start by checking for a vacuum leak while the engine is running at rough idle.
     
  9. FerrariMech1

    FerrariMech1 Karting

    Dec 14, 2014
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    #1 matches my remedial action perfectly



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  10. FerrariMech1

    FerrariMech1 Karting

    Dec 14, 2014
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    Sorry, it’s a US car with all the emission stuff removed. No air pump, manifold ports blocked off, etc... the only thing that is still in place is the EGR


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  11. FerrariMech1

    FerrariMech1 Karting

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    Is it possible that the EGR is sticking open?

    I know they are normally only open at idle but I’m sure it’s possible that the WOT is causing some sort of malfunction with the device

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  12. Steve Magnusson

    Steve Magnusson F1 World Champ
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    That's not bad news IMO - and seems more like an upstream control problem than anything wrong with the WUR or fuel distributor themselves.

    Let me have a peek at your OM this afternoon to refresh my memory about your EGR system and operation. My memory is that there is an electrovalve involved in the control of the EGR valve so you might be able to deduce (or force) something there about the EGR system working or not working
     
  13. FerrariMech1

    FerrariMech1 Karting

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    #13 FerrariMech1, Mar 13, 2018
    Last edited: Mar 13, 2018
    There’s a three outlet electro valve in the circuit. One end goes to the top of the throttle body, another to the EGR, and last one goes to another electrovalve on the front bank which goes to who knows what...

    I’m going to try and work on blocking off the EGR ports (or taking away the vacuum) to see if that changes anything


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  14. johnk...

    johnk... F1 Veteran
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    Yes, it's a typical temperamental Italian. DO you go to the doctor every time you sneeze?
     
  15. tatcat

    tatcat F1 Veteran
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    Do you still have the cat
    Sometimes after a hard run it can overheat and cause problems
     
  16. Steve Magnusson

    Steve Magnusson F1 World Champ
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    That sounds ideal. Pages N11-N14 in the 281/83 Mondial8/QV WSM would be your best reference (downloadable from http://ferrari.cdyn.com). At warm idle, there should be no vacuum applied to the EGR valve diaphragm so you can just unplug the vacuum line going to it to force that condition. If the EGR Valve itself is just (wrongly) remaining stuck open after returning to warm idle (with no vacuum applied), then blocking off the exhaust gas path some other way would be a good test. Good hunting!
     
  17. ME308

    ME308 Formula 3
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    me too was thinking of that ...
    but how does one explain then, that the idle is immediately smooth after a hot re-start ?

    if the egr valve where to be stuck open during the time the engine exceeds 5000rpm, I`d guess it would stay that way even after a shut down & immediate re-start

    anyway, taking the egr valve completely out of the game would be good start ;)


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  18. johnk...

    johnk... F1 Veteran
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    When the car is idling badly just get out and tap the EGR valve and see if it evens out, or pull off the vacuum line and hold your finger over it.
     
  19. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Agree that's an unlikely scenario, but even something like the starter motor cranking might give enough vibration to get it unstuck (so johnk...'s suggestion to just it it a whack seems a logical first step). I was hoping that the OP could first confirm that his EGR system configuration still matches the figure on page N11 (since he reported a lot of other emission modifications): Image Unavailable, Please Login
     
  20. FerrariMech1

    FerrariMech1 Karting

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    Steve, the configuration noted here is the exact way it is set up. Albeit, the only thing that could potentially be a problem is the electrovalve and the temp sensor... I have no clue if they still work


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  21. FerrariMech1

    FerrariMech1 Karting

    Dec 14, 2014
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    So, I went ahead and removed the vacuum line at the EGR and plugged both the EGR itself and the tap on the throttle body. Took it for a drive getting it nice and hot before putting the car through its paces.

    I was beginning to think I was in the clear after going at it for half hour or so until it decided to misbehave. It did so in the same way as described before... giving the EGR a good whack didn’t seem to change anything

    Back to the drawing board!

    PS: I’ll try to get some video the next time I go out


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  22. jcurry

    jcurry F1 Veteran
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    Long shot, but maybe the valve is set at too low of vacuum and the exhaust is opening it slightly even when disconnected. There is a set screw on top to adjust the spring.
     
  23. FerrariMech1

    FerrariMech1 Karting

    Dec 14, 2014
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    Is that what that is? Ill try and fiddle with it to see if that changes anything.

    Thank you!


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  24. FerrariMech1

    FerrariMech1 Karting

    Dec 14, 2014
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    Jcurry mentioned something about the throttle bypass valve which had the “tail” incorrectly routed to the plenum instead of the electrovalve.

    I really need to work on removing the EGR before I can move on. Does anyone have any ideas on plugs for the intake outlet?


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  25. jcurry

    jcurry F1 Veteran
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    not me, but let us know if that fixes things
     

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