355 - Misfire and strange rpm problems | FerrariChat

355 Misfire and strange rpm problems

Discussion in '348/355' started by lanab, Jul 29, 2022.

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  1. lanab

    lanab Formula Junior

    Feb 21, 2016
    510
    Stockholm, Sweden
    Started to get strange rpm problems, when i start the car i notice it's not running as it should, feels like missing one cylinder or two, pretty high gas smell also from exhaust back of the car.

    When i start driving it's very hard to keep rpms down as it starts to climb without pressing the gas pedal, when i drive it judders a bit from time to time but when i stop the rpm won't go down to idle but stays at around 2000 rpm, after a half a minute it starts to fall down to correct idle rpm when i stand still.

    The car is serviced recently and HT cables are replaced, new spark plugs, O2 sensors and new exhaust ECUs.

    It seems the car gets too much fuel or like when you run a car on choke as the rpm behaves very strange as sometimes it wants to accelerate by it's own very slowly climbing rpm, could it be MAF?

    Yesterday i drove it hard for a long time and the problems went away, but probably it will come back if i start it from cold again......
     
  2. Qavion

    Qavion F1 World Champ
    Silver Subscribed

    Feb 20, 2015
    14,262
    Sydney
    Full Name:
    Ian Riddell
    One of the best ways to see if the MAF is causing an issue is to simply disconnect it. This forces the car to use other sensors to control fuel. If the MAF was really bad, the engine should show some improvement.

    2000 rpm seems pretty high. I don't know how you would get to those rpms except by actually introducing more air into the engine. Sticky throttle cable/throttle bodies? I'm not sure how it ties in with all the other symptoms though.
     
    lanab likes this.
  3. lanab

    lanab Formula Junior

    Feb 21, 2016
    510
    Stockholm, Sweden
    Yes it seems strange, it get stucked at 2k rpm and then moves slowly down to idle, could be the ICVs, i will remove them and clean them up.
     
  4. yelcab

    yelcab F1 World Champ
    Consultant

    Nov 29, 2001
    13,547
    San Carlos, CA
    Full Name:
    Mitchell Le
    If it were serviced recently, you should take it back. There are way too many reasons for this car to misfire and run like crap.
     
    Ed Russell likes this.
  5. lanab

    lanab Formula Junior

    Feb 21, 2016
    510
    Stockholm, Sweden
    No i did everything myself, i am restoring exotics so i can only go back to myself:D

    I have cleaned the ICVs now, i might suspect water in the spark plug holes as i forgot to cover the engine the last time.
     
  6. Qavion

    Qavion F1 World Champ
    Silver Subscribed

    Feb 20, 2015
    14,262
    Sydney
    Full Name:
    Ian Riddell
    I thought about ICVs, but I don’t understand why they would cause a strong gas smell.
     
  7. Targatime

    Targatime Formula 3

    Feb 22, 2014
    1,449
    Los Angeles
    You're sure the throttle cable or bellcrank aren't sticking?
     
  8. lanab

    lanab Formula Junior

    Feb 21, 2016
    510
    Stockholm, Sweden
    I have checked and replace throttle cable one month ago, can't see any sticking problems, didn't have any issues after that.

    The gas smell i've always had when starting from cold, never any issues before, the smell is not from engine bay but from the exhaust tips, completely restored the whole fuel system when i restored the car, however the misfires are a bit odd as they went away when i have driven for a while, could be old fuel from last year but i filled her up recently...
     
  9. Ferrarium

    Ferrarium F1 Veteran
    Sponsor Rossa Subscribed

    Jul 28, 2018
    5,728
    Central NJ
    Full Name:
    Eric
    Gas smell when cold, fuel pressure regulator stuck or leaky injector(s)?
     
    lanab likes this.
  10. yelcab

    yelcab F1 World Champ
    Consultant

    Nov 29, 2001
    13,547
    San Carlos, CA
    Full Name:
    Mitchell Le
    there should be a misfire code in the DME
     
  11. lanab

    lanab Formula Junior

    Feb 21, 2016
    510
    Stockholm, Sweden
    Working great now after i cleaned the ICVs, rock stable idle and not sticking, no misfire, could be a combination of old fuel as well but it works now
     
    Qavion likes this.

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