355 flat spot off idle | FerrariChat

355 flat spot off idle

Discussion in '348/355' started by strosek, Jun 30, 2011.

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  1. strosek

    strosek Karting

    Sep 23, 2010
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    Arkansas, USA
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    Eric
    #1 strosek, Jun 30, 2011
    My 96 355 has a very bad flat spot just off idle, it is most noticeable when the motor is still cold. If you lightly push on the gas pedal the rpms will drop and the motor will sound like it is dropping a cyl. After it is warm it will accerate good but it is still there between shifts. When you shift and release the clutch there is a slight lull in power coming back. The car is new to me and has been doing this since I got the car. I also feel it is a litt;e low on power. It does not feel like 380 horses to me.
    Thanks,
    Eric
     
  2. plugzit

    plugzit F1 Veteran
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    Dec 1, 2004
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    Bruce Bogart
    #2 plugzit, Jun 30, 2011
    Probably vacuum leak, possible throttle body mistune.
     
  3. strosek

    strosek Karting

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    Eric
    #3 strosek, Jun 30, 2011
    fuel trim looks good. Throttle adjust might be it. I was wondering about a partial plugged exhaust. That would explain the low power and possibly the flat spot.
    Eric
     
  4. plugzit

    plugzit F1 Veteran
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    Bruce Bogart
    #4 plugzit, Jun 30, 2011
    Plugged exhaust would get worse as rpms increase. Wha you describe sounds like a vacuum leak. Check throttle position sensors after you check for vac leak.
     
  5. strosek

    strosek Karting

    Sep 23, 2010
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    Eric
    #5 strosek, Jul 1, 2011
    I thought about TPS, but the WSM sayes they are only used at idle and wide open throttle unless the MAF is bad.
    Eric
     
  6. jm3

    jm3 F1 Rookie

    Oct 3, 2002
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    JM3
    #6 jm3, Jul 2, 2011
    Sync throttles. That is all.
     
  7. tbakowsky

    tbakowsky F1 World Champ
    Consultant Professional Ferrari Technician

    Sep 18, 2002
    19,379
    The Cold North
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    Tom
    #7 tbakowsky, Jul 2, 2011
    check your manifolds for leaks, and your cats for clogging/breaking apart. Both will cause the issue you are having. TPS?? doubt it...
     
  8. Philippe

    Philippe Karting

    Nov 2, 2003
    68
    Brussels, Belgium
    #8 Philippe, Jul 3, 2011
    Got the same problem one month ago on my 99 f355. Throttles (butterflies) were out of sync. The spark plugs have been changed as well. Everything is fine now.
     
  9. PAP 348

    PAP 348 Nine Time F1 World Champ
    Lifetime Rossa Owner

    Dec 10, 2005
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    Pap
    #9 PAP 348, Jul 3, 2011
    Good to hear. That is what the OP's problem is too I reckon. :):)

    Balance the throttle-bodies and it should fix the problem. :):)
     
  10. strosek

    strosek Karting

    Sep 23, 2010
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    Eric
    #10 strosek, Jul 3, 2011
    Thanks I will balance the throttles and let you know. What kind of gauge are you using to do this? I have a uni sync for carbs, but I would have to pull the upper plenum to use it.
    Thanks,
    Eric
     
  11. PAP 348

    PAP 348 Nine Time F1 World Champ
    Lifetime Rossa Owner

    Dec 10, 2005
    99,341
    Mount Isa, Australia
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    Pap
    #11 PAP 348, Jul 3, 2011
    You need to buy/borrow/steal a mercury gauge for this job mate. :D:D

    **Try and borrow one first** :eek::eek:
     

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