355 engine cut off at 2500 RPM | FerrariChat

355 engine cut off at 2500 RPM

Discussion in '348/355' started by hameednoor, May 18, 2015.

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  1. hameednoor

    hameednoor Rookie

    Jun 4, 2010
    21
    Hi,
    I have a 1997 355 GTS. The following problem cropped up out if the blue. As soon as I reach about 2500 RPM, the engine cuts off, check engine and slow down lights come on. Release the throttle and everything back to normal. All lights off. Accelerate again and same thing. Same thing hot or cold.

    I don't have cats and have disconnected the sensors. So my check engine light has always been flashing. Only recent work was to change oil and put in a new battery.

    Mechanic saw a leaking breather and fixed it. Problem continues but at 4000 RPM and when warm. Plug wires ok. No error codes. Still diagnosing but drawing a blank. HELP!

    Regards
    Hameed
     
  2. ready321now

    ready321now Formula Junior

    Jan 5, 2013
    484
    New Jersey
    Does it do it while revving the engine in neutral? it's interesting that it moved from 2500 to 4000. That alone should indicate something. I'm not sure but it might be possible that one engine bank is cutting since the slow down light is on. Is it blinking or is it solid?
     
  3. ready321now

    ready321now Formula Junior

    Jan 5, 2013
    484
    New Jersey
    is it possible that 1 of your thermocouples is giving a wildly inaccurate temperature reading because it is faulty? that might send the engine straight into limp mode where it is running on four cylinders only. A simple thing you can do is unplug all of the associated ECU's and clean the connections.
     
  4. Prugna

    Prugna Formula 3
    Silver Subscribed

    Nov 13, 2014
    2,005
    Northern California
    Two things:

    First I would look for a plug wire to be touching a header or pipe somewhere.
    Second I would look for water down in the spark plugs (under the covers).
     
  5. drbob101

    drbob101 F1 Rookie
    Owner Silver Subscribed

    Nov 26, 2012
    3,821
    Tinton Falls, NJ
    Full Name:
    Bob Ferraris
    I dont know what you mean that you have disconnected the sensors.

    My testing shows that an unplugged Thermocouple will will output 5V from cat ecu and trigger a bank shut down. If you unplug the ecu there is a bias voltage of 5V as well.

    How long has the Cat monitoring system been disabled and when did you unplug things>
     
  6. eyboro

    eyboro Formula Junior
    Silver Subscribed

    May 30, 2004
    989
    Chicago
    Full Name:
    Eitan
    Look in your engine compartment and make sure all the air intake pipes are connected on top of the engine, if one is loose or disconnected, you will have a problem.
     
  7. hameednoor

    hameednoor Rookie

    Jun 4, 2010
    21
    Yes it happened in neutral also. It is not one bank. I know how that feels. Light was solid.
    Thanks
     
  8. hameednoor

    hameednoor Rookie

    Jun 4, 2010
    21
    Thanks. mechanic checked that and fixed a minor leak. That is how the RPM moved from 2500 to 4000
     
  9. hameednoor

    hameednoor Rookie

    Jun 4, 2010
    21
    Thanks. CAT monitoring system disconnected for a year now. That is what I meant by disconnected sensors
     
  10. hameednoor

    hameednoor Rookie

    Jun 4, 2010
    21
    Thanks all. Will check and keep you updated
     
  11. drbob101

    drbob101 F1 Rookie
    Owner Silver Subscribed

    Nov 26, 2012
    3,821
    Tinton Falls, NJ
    Full Name:
    Bob Ferraris
    You will get limp mode voltages sent to the ecu with the system disconnected. I cannot explain why you haven't had this in the past year but if you check the voltages on the signal lines to the main ecu from the disconnected cat ecu s you will probably find 5V.

    5V will trip the slow down system. I suggest you look into this first.
     
  12. SoCal1

    SoCal1 F1 Veteran
    Owner Silver Subscribed

    Jun 14, 2011
    8,630
    SoCal LA/OC/New Mexico
    Full Name:
    Tim Dee
    Yikes

    May have fried the ecu

    I would check every connection. When cold it should not go into limp and should rev normally

    Try disconnect battery for a few min and see if you can get it to rev, if not your best bet is an SD tool or try swapping a computer with a known good one
     
  13. F355Bob

    F355Bob Formula 3

    What about a bad throttle position switch. My 95 would go into limp mode even when stone cold when I had a bad cat ECU but you have yours disconnected.
     
  14. hameednoor

    hameednoor Rookie

    Jun 4, 2010
    21
    NO luck Yet! Can't diagnose
     

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