355 5.2 Idle control valve | FerrariChat
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355 5.2 Idle control valve

Discussion in '348/355' started by pourquoi_ne, Apr 13, 2010.

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  1. pourquoi_ne

    pourquoi_ne Karting

    Mar 16, 2006
    224
    England
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    John
    #1 pourquoi_ne, Apr 13, 2010
    I have an annoying misfire on tick over which comes and goes. I had a look at the idle control valve today. When I look into the valve end I can see a kind of rotor which moves freely when the body is turned sharply. I plugged it back into the loom and turned on the ignition. Nothing happened to the valve - it was still free to move but the body of the whole unit was vibrating slightly. Does the valve operate when engine is cranked/started? Or have I a problem? Have searched the forum for answers but couldnt find anything.

    Any thoughts please, Guys?
     
  2. J. Salmon

    J. Salmon F1 Rookie
    Owner Rossa Subscribed

    Aug 27, 2005
    4,367
    VA
    #2 J. Salmon, Apr 13, 2010
    I don't know exactly how the system is setup here, but in general the idle air control system maintains idle speed when a load is placed on the engine at idle, such as the AC compressor. It lets air bypass the throttle plates, which remain closed.

    So I would let the car idle and turn on/off the AC compressor and see if that has any effect.
     
  3. eric355

    eric355 Formula 3
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    Eric DECOUX
    #3 eric355, Apr 14, 2010
    I think you are OK.
    The idle regulator is driven by 2 electrical signals from the Motronic. One try to open the valve, the second try to close it. The Motronic sends very quick open/close orders (probably around 70Hz) to adjust the position of the valve according to idle RPM. So it is quite normal you feel some vibrations in the body. The torque applied to the rotating part is also quite small so it can feel free again when you move the body.
    If your idle speed is constant around 1050 RPM, I don't think you have any problem there.
     
  4. pourquoi_ne

    pourquoi_ne Karting

    Mar 16, 2006
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    #4 pourquoi_ne, Apr 14, 2010
    Merci Eric! Explains the situation totally! I would still like to get a better tickover though. Mine is ok when cold but when hot sometimes its ok other times there is a distinct misfire. Plug leads perhaps?
     
  5. eric355

    eric355 Formula 3
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    Nov 30, 2005
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    Eric DECOUX
    #5 eric355, Apr 14, 2010
    Plug leads, plugs, coils or may be throttle bodies balancing .... It could be a lot of different things.
    If your plug leads are still the original ones, they could be the favorite culprits.
     
  6. Jelly Spanners

    Jelly Spanners Karting

    Jul 19, 2009
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    South West UK
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    Jeremy
    #6 Jelly Spanners, Apr 14, 2010
    Ihad this with my 1997 355 and found a hole in one of the metal idle valve by pass pipes that come from the by pass valve to each side plenem, search for by pass metal pipes and see my thread, the left hand pipe had rubbed through on the cylinder head cam cover where it had been fitted incorrectly, I have put a link to the thread but dont know if it will work

    Hope this helps

    http://www.ferrarichat.com/forum/showthread.php?t=261421&highlight=355+idle+valve+pipes
     
  7. saw1998

    saw1998 F1 Veteran

    Jun 8, 2008
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    Scott
    #7 saw1998, Apr 14, 2010
    That was a very helpful thread, Jeremy. Thanks again.
     
  8. f355spider

    f355spider F1 World Champ
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    May 29, 2001
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    #8 f355spider, Apr 14, 2010
    +1 on plug wires and also plugs themselves. Watch out for water leaking into the plug wells either through the back side where the wires enter (foam block could be missing) or just improper sealing of the metal covers. I had a water leak which caused a miss. New plug and resealed covers fixed it right up.

    New wire sets are available from www.kingsborne.com at reasonable prices, and they use oem Beru connectors on each end of the wire.
     
  9. pourquoi_ne

    pourquoi_ne Karting

    Mar 16, 2006
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    #9 pourquoi_ne, Apr 15, 2010
    Thanks Guys! I have had checked the metal bypass pipe and found them to be OK! I am going to check out the plug leads next!
     
  10. f355spider

    f355spider F1 World Champ
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    #10 f355spider, Apr 15, 2010
    John, pull the plugs and inspect them...I actually had one that was rusty on the outside from the water leaking into the plug wells.
     

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