Erratic idle- Mondial QV | FerrariChat

Erratic idle- Mondial QV

Discussion in 'Mondial' started by ssrealty, Aug 5, 2016.

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  1. ssrealty

    ssrealty Formula Junior

    Sep 12, 2010
    325
    Austin, TX
    Full Name:
    Chris Warren
    I have an erratic idle, especially when cold. It does not do it all of the time. Below is a video link:

    https://youtu.be/SdKQGdDbA0w

    Any ideas?
     
  2. moysiuan

    moysiuan F1 Rookie
    Silver Subscribed

    Nov 1, 2005
    3,628
    Canada
    Seeing how it seemed to stop after you tapped the throttle, my guess is the throttle position sensor either needs adjustment or has failed and is giving incorrect resistance signals. The surging is the computer somehow getting wrong signals, richening the mixture, overcompensating and than adjusting back.

    I recall someone had low coolant and air in the coolant, which can give some odd readings when the computer is measuring coolant temps, so might be worth checking/bleeding, can"t do any harm!
     
  3. ssrealty

    ssrealty Formula Junior

    Sep 12, 2010
    325
    Austin, TX
    Full Name:
    Chris Warren
    I know the TPS switch was replaced recently, and new coolant was installed this spring.

    Isn't there a crank sensor as well?
     
  4. BOKelley

    BOKelley Formula 3
    Silver Subscribed

    Jul 5, 2009
    2,058
    Au'n Colorado
    Full Name:
    Brock
    Is yours a 3.0 liter? If so then you have 3 crank sensors .... If 3.2 then only two. However, your idle is erratic on the high side which leads me to think the problem is with the FI... Warm up regulator perhaps or maybe the air flow sensor plate is not properly centered and is hanging up until you blip the throttle??

    Brock
     
  5. spicedriver

    spicedriver F1 Rookie

    Feb 1, 2011
    3,859
    Maybe the cold start injector is leaking. Try removing it, and cover the hole with duct tape.
     
  6. Bell Bloke

    Bell Bloke Formula 3

    Dec 6, 2012
    1,839
    UK
    First things first, you need to look at the spark. I have a similar problem which when I get time I will fix.
    Here is my diagnosis, it took me about 20 mins to track down the problem to a spark timing issue at idle.

    https://www.youtube.com/watch?v=lX0vwhlDSVE&feature=youtu.be

    1.Get a strobe light
    2.Mark your crank damper with a white maker at TDC on piston 1 and TDC on piston 5.
    3.Measure as I have in the video.
    4. If all is as it should be then it's fuel.
    Good luck, Bell bloke.
     
  7. mike32

    mike32 F1 Veteran

    May 13, 2016
    5,828
    Isle of man- uk
    Check the run of the throttle cable as it can foul the carpet , if no better try some redex or similar injector cleaner in the tank
     
  8. ssrealty

    ssrealty Formula Junior

    Sep 12, 2010
    325
    Austin, TX
    Full Name:
    Chris Warren
    Mine is a 308 QV.

    Warm up regulator was also replaced with a rebuilt unit a couple of years ago. This erratic idle also occurs when driving and engine is warm. So, it is not limited to when engine is cold or at startup.
     
  9. BOKelley

    BOKelley Formula 3
    Silver Subscribed

    Jul 5, 2009
    2,058
    Au'n Colorado
    Full Name:
    Brock
    Ok, being a 3.0 liter that means you have three sensors...so to Bell Blokes' point, let me ask this question as it was difficult to hear the engine running in your video.....When your tachometer indicates erratic rpm you can hear the engine revs fluctuate too, correct? And the erratic idle revs are higher than the normal idle speed, yes?
     
  10. ssrealty

    ssrealty Formula Junior

    Sep 12, 2010
    325
    Austin, TX
    Full Name:
    Chris Warren
    Well I took the Mondial in for service. The erratic idle mirrored the engine RPM as well. So, the engine RPM did fluctuate like the tachometer.

    We initially thought it may be the crank sensors, but the three sensors checked out OK. My mechanic checked out one of the distributor caps, and the rotor was not properly installed, and there was moisture in the cap. So, we replaced the rotor, cap, and spark plug wires. This appears to have fixed the problem. No erratic idle so far.

    One thing about Ferraris. You can spend a lot of time replacing parts that don't fix the problem. And even supposed Ferrari shops don't get it right. I have spent a lot of money on repairs and mechanics who made repairs, and I have had to pay other mechanics to fix what they sometimes could not repair. Sometimes, they also did not repair properly. For example, I paid to repair shift shaft seal and new oil pan gaskets. The mechanic did not use the right sealant, and the oil pan gaskets are leaking again. Will have to pay to redo this job but will wait until next year.
     
  11. BOKelley

    BOKelley Formula 3
    Silver Subscribed

    Jul 5, 2009
    2,058
    Au'n Colorado
    Full Name:
    Brock
    Excellent, it sounds like it was a relatively easy repair....good to hear what the problem was!

    Brock
     

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