328 running issue during warm up | FerrariChat
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328 running issue during warm up

Discussion in '308/328' started by pad, Oct 12, 2023.

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  1. pad

    pad Formula 3

    Sep 30, 2004
    1,426
    Tequesta, FL
    Full Name:
    Paul Delatush
    #1 pad, Oct 12, 2023
    I need to tap into the FC Brain Trust. I have the following issue: My ’86 USA 328 is stock with the exception it has no cats. There is a new OS sensor in the cat delete pipe, but no Thermo sensor. The WUR, throttle position switch, spark plugs, extender, wires, distributor caps have been replaced along with the fuel injectors. Vacuum lines are new. Also replaced are the fuel pump and fuel filter. The warm up control located under the water expansion tank has been removed and tested OK.

    The car runs great once warmed up. The problem is the running just after that warm up period. Upon starting, the car runs at 1800 RPMS and drops down to 1200 RPMS after about 2 minutes. When I take off at that point, the car has very little power and sometimes ever backfires. It acts as if 1 or 2 plugs are fouled. This condition can last up to 10 minutes. After that the car starts and runs great all day. I should note that I am located in SE Florida with the weather being between to upper 70F to 90F. I have run the car with aux fuel injector located on the right side of the intake plenum connected and disconnected with no difference. I have also adjusted the fuel distributor, which has effected the idle smoothness, but not the overall running condition. The car has 55K miles.

    I look forward to your comments. Thanks, Paul
     
  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,819
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #2 Steve Magnusson, Oct 12, 2023
    I think you, unfortunately, win the "that's a new, weird problem that's never been reported before" contest AFAIK.

    One easy thing to do is just confirm/deny that you have spark on both banks during the bad running time (although would seem strange that hot is better than cold).

    Also, what is the status of your air injection system? Have you checked for any holes/leaks in the air injection manifolds and/or check valves and/or hoses downstream of the cut-off valve? One easy thing to do here is just unplug the single wire of the O2 sensor (which forces it into open-loop mode) -- if that runs better = shows something is "confusing" the closed-loop mode.
     
    RodC328gts likes this.
  3. theunissenguido

    theunissenguido F1 Rookie
    Owner Silver Subscribed

    Jan 21, 2004
    2,668
    Argent/Brasil
    Full Name:
    Guido
    #3 theunissenguido, Oct 12, 2023
    Could be a humidity issue...Florida ! Once warm the humidity is gone...
     

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