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355 Idle unstable

Discussion in '348/355' started by fck, Feb 20, 2010.

  1. fck

    fck Rookie

    Jan 21, 2010
    31
    HK
    Hi all, my 1997 manual F355 berlinetta today have the below problem, normally when I stop it at traffic jam or traffic light the ldle will back to around 1,000 rmp and stable, but today I got four traffic lights also have the problem was the idle back to around 1,000 rmp, when I still wating for the light have not pick up around 10 seconds later the rmp suddenly drop to around 500 rmp, I saw the oil pressure also drop together and the red light on from the oil pressure gauge and the car almost off due to the rmp too low who know whats problem? Is it the air mass sensor dirty or the idle regulator almost die?
     
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  3. tendeu

    tendeu Karting

    Dec 1, 2009
    66
    Good Afternoon, the problem of your car might be in the oil pump or fuel pump.
     
  4. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    17,268
    USA
    Full Name:
    Hugh G. Rection
    Unlikely. The low oil pressure is a symptom of the low idle.

    First, you need a better diagnosis. Does the idle drop coincide with the fans kicking on? There is a common problem; as the SPAL brand radiator fans get older, they draw excessive current, and when they kick on, the extra current draw at idle, (which makes the alternator work very hard) can cause the idle drop. One thing to check, the stock fuse for the fans is 30amp...have they been blowing? If not, check them, sometimes owners and dealer techs will replace the fuses with 40amp...which solves the fuse blowing, but they the idle problem can crop up. The solution is to replace the fans.


    If you are not seeing a connection with fan operation, then two other things to check. Removed and clean the idle control motor, they can sometime get 'sticky' in operation from blow by. Remove and flush with some carb cleaner spray in each end and make sure the valve moves easily inside.

    I had a minor idle stability issue a couple years ago, and found the plug on to my MAF was not good. Cleaning the plug contacts improved things temporarily, but I had the dealer replace the pins, all good now....but my idle drop was only 150 rpms or so. Try cleaning the plug connections to the MAF...but I doubt this is your issue.
     
  5. 355Aussie

    355Aussie Formula Junior
    Rossa Subscribed

    Jul 3, 2007
    634
    Sydney
    Full Name:
    George
    The problem is in the idle regulator. Try and get someone to lend you one and see if it happens as a process of elimination.
     
  6. Loser

    Loser Formula Junior

    Apr 11, 2008
    791
    Gilroy, CA
    Full Name:
    Tom
    Is the car running open-loop? I had this problem with my 97 Spider and when I checked the codes, I had quite a few. It seemed that after I replaced my O2 sensors and the car started running closed loop again, the problem went away. You can check your codes with an OBDII reader such as the EQUUS 3100A. Normally, you would get a check-engine light in open-loop mode, but in my case a previous owner had removed the bulb from the check-engine indicator and installed test pipes in place of the catalytic converters.
     
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  8. fck

    fck Rookie

    Jan 21, 2010
    31
    HK
    Thankyou all, I will follow you guys the advise to check it and give you the answer.
     
  9. MarkCollins

    MarkCollins F1 Rookie
    Owner

    Jul 2, 2002
    3,199
    South England
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    Mark Collins
    The idle air valve can come loose from it's position allowing additional air in after the MAF, make sure it's seated correctly
     
  10. sambomydog

    sambomydog Guest

    May 23, 2009
    1,367
    Also just check that the rubber tubing from the airflow meters/meter to the plenum has no splits in it. Thus allowing/drawing extra air into the system, (similar to what MarkColins suggested). One of mine was split were the clamp bit into the rubber, and mine ran uneven. This also is the cause for rough idling.
     
  11. race850i

    race850i Karting

    Jan 6, 2010
    132
    Germany
    Full Name:
    Themis
    If you clean the idle control motor,what I think is your issue dont forget after the install to reprogramme it.What I mean, this motor is a self learning motor.
    After the install schitch all the electrik/electronik off from the car, start the engine and let him work on Idle for about 10 min, on this time the ECU will reprogramm the motor to work properly!!
    Otherwise if you dont do that drive the car and operate the A/C the Idle will be still anstable!

    wish you good luck
    Themis
     
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  13. fck

    fck Rookie

    Jan 21, 2010
    31
    HK
    Today I try to check it again, when the idle drop 1 to 2 seconds later the fans kicking on so I believe f355spider the advise is possitive so I will try to get two 40amp fuses to replace the existing two 30amp fuses let see is it can fix the problem, but where is these two fuses locate? I checked it was not in the front compartment.
     
  14. f355spider

    f355spider F1 World Champ
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    #11 f355spider, Feb 22, 2010
    Last edited: Feb 22, 2010
    NO! You need to replace both radiator fans....not the fuses. The fans are out of spec, and drawing too much current...which causes the alternator to work very hard, causing the idle to drop

    This is the best price for the fans (you need two) http://www.the-fan-man.com/shop/size-pull-part-2049-p-219.html?osCsid=c5b9027f5137ba744d1d40e666124cd1
    These do NOT come with the Ferrari 355 specific electric plug, so you will have to cut the old one of your existing fan, and splice it onto the new fan. Worth the trouble, these are otherwise identical, but hundreds of dollars less costly.

    I would recommend you remove, clean and inspect your Idle Control Valve, just to be certain that is not contributing to your problem.
     
  15. fck

    fck Rookie

    Jan 21, 2010
    31
    HK
    I have talk with factory today and they said they have experience for this case before although they changed the new fans also cannot fix it, the battery or alternator get old also will have same problem so they need to do the full check can figure out what problem.
     
  16. WillW

    WillW Karting
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    May 23, 2005
    205
    Helsinki, Finland
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    Ville
    If 355 have same idle control valves as 348, I could bet that they need cleaning/changing. (I have had same prob in 2 348's and they were idle control valves. Very easy to change DIY)
     
  17. fck

    fck Rookie

    Jan 21, 2010
    31
    HK
  18. f355spider

    f355spider F1 World Champ
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    May 29, 2001
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  19. fck

    fck Rookie

    Jan 21, 2010
    31
    HK
    Just went to garage to clean the idle regulator but have not much improve, the machinist used the meter to checked the fans drawn the current is very stable when kicking on with no heat and any noise, so he presume it is the ground cable ( one from battery to ground and another one from Engine to ground ) got old or the plug oxidizied will make the idle unstable. If so change the new one or tailor make the thicker one to replace it will be okay.
     
  20. WillW

    WillW Karting
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    May 23, 2005
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    Ville
    #17 WillW, Feb 27, 2010
    Last edited: Feb 27, 2010
    Exactly, at least in 348 those ones are Bosch units, I paid something like 140$ each. (I assumed grounding was already checked, that would be cheap fix and should be done anyway)
     
  21. f355spider

    f355spider F1 World Champ
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    Check operation of MAF as well and try cleaning the connection to it.
     
  22. Loser

    Loser Formula Junior

    Apr 11, 2008
    791
    Gilroy, CA
    Full Name:
    Tom
    If you haven't done so already, I still think you should check for codes and if the system is running open loop.
     
  23. fck

    fck Rookie

    Jan 21, 2010
    31
    HK
    Just pick up the car from garage and the machinist said he checked the battery and alternator the output are very stable, the fans running very well no overload when kicking on drawn the current. After he cleaned the idle regulator, polished ground cable plug and the fans cable plug now get better, when the fans kicking on it drop to around 800 rmp, after few seconds will back to around 1000 rmp better than previously drop to around 500 rmp make the engine almost down.
     
  24. fck

    fck Rookie

    Jan 21, 2010
    31
    HK
    Finally I have ordered the new fans wait for arrive to change it and will update you guys.
     
  25. fck

    fck Rookie

    Jan 21, 2010
    31
    HK
    After changed two fans the problem fixed already thankyou so much for f355spider the advise, also I order the fans from the company in USA more cheaper than I order from local agent.
     
  26. f355spider

    f355spider F1 World Champ
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    May 29, 2001
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    Glad to hear it is fixed, thank you for posted the final resolution to your problem. :)
     
  27. Vegas-Guy

    Vegas-Guy Formula 3

    Nov 25, 2007
    1,817
    Austin, TX
    Full Name:
    Reg
    Great news..:)
     

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