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328 Idle Issue

Discussion in 'Technical Q&A' started by Freestyle, Dec 30, 2007.

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  1. Freestyle

    Freestyle Rookie

    Dec 24, 2007
    21
    #1 Freestyle, Dec 30, 2007
    When I start my 328 the cold start valve opens up and the car idles at a higher rpm, as it should, until the engine is warm. Then the idle drops back down to around 1100 rpms, but only stays there for a couple of minutes. The engine then rev's up to around 2000 rpms and stays there whenever I'm at idle. Sometimes punching the gas pedal seems to alleviate the problem, but only temporarily. It will rev back up suddenly without any input from myself. I did replace the O2 sensor recently with a Bosch replacement that has seemed to work well. Maybe I need a new throttle switch, cold start valve? How about the ECU? Any input would be well appreciated. Thx!
     
  2. yelcab

    yelcab F1 World Champ
    Consultant

    Nov 29, 2001
    13,586
    San Carlos, CA
    Full Name:
    Mitchell Le
    #2 yelcab, Dec 30, 2007
    welcome to CIS hell.

    There are a few easy ones to check first:

    1. Throttle cable, did you mess with it? Is it too tight?
    2. You can also adjust the idle speed on the car for when it is warm.

    Beyond the easy ones, it gets harder to diagnose. Bypass valve gets sticky?

    Then, you will need to do some kind of a fuel pressure test to find out what the system pressure is, and the control pressure is. Need a test rig for that.

    That is all I can tell you right now without a little more information about what else is going on.
     
  3. Freestyle

    Freestyle Rookie

    Dec 24, 2007
    21
    #3 Freestyle, Dec 30, 2007
    Thanks for you post. I did not touch the throttle cable and it appears to be working just fine. The rubber hose from the driver's side (left) rear valve cover was recently disconnected by a Ferrari mechanic who forgot to retighten one of the hose clamps, and so it was leaking quite a bit of oil and I would assume some vacuum pressure. Other than that, nothing has been changed. It does seem like there is a sticky valve operation which works infrequently.
     
  4. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,841
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #4 Steve Magnusson, Dec 30, 2007
    Is this a US version 328? (since you said "O2 sensor", I assume it is, but please confirm).

    You need to start ruling out things that can let extra air into the intake tract -- the throttle cable/plate is the first one to check, next would be to test the AAV (by pinching one of the air lines closed when warm and you've got the high warm idle condition -- if the idle drops back to normal, the AAV is bad because it should always be fully closed when warm; if the idle doesn't change and stays high, the AAV is probably OK).

    You should be able to check the throttle microswitch with an Ohmmeter -- i.e., pin 2 should be connected to pin 18 when the throttle plate is at the idle position -- see this thread:

    http://ferrarichat.com/forum/showthread.php?t=175987
     
  5. wetpet

    wetpet F1 World Champ
    BANNED

    May 3, 2006
    10,210
    #5 wetpet, Dec 30, 2007
    i have the same prob periodically. idle speed adjust works for me.
     
  6. Freestyle

    Freestyle Rookie

    Dec 24, 2007
    21
    #6 Freestyle, Dec 31, 2007
    Thanks for the posts, I appreciate the input. My 328 is a 1988 US version car, before anti-lock brakes.
     
  7. KKRace

    KKRace Formula 3

    Aug 6, 2007
    1,052
    Rockville/Olney MD
    Full Name:
    Kevin
    #7 KKRace, Jan 2, 2008
    Check the Italian Cruise Control(floor mat under gas pedal).
     
  8. Mule

    Mule F1 Rookie
    Owner Rossa Subscribed

    Jun 25, 2003
    3,758
    Alaska
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    Mule
    #8 Mule, Jan 2, 2008
    And get some of Birdman's mat grabbers if that is the problem. Worked for me with the same symptoms.
     

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