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Loss most of the power

Discussion in 'Technical Q&A' started by mahlerfree, Dec 3, 2020.

  1. mahlerfree

    mahlerfree Rookie

    Dec 19, 2019
    41
    the 360 Modena's diagnostic computer shows p1149 and p1189 on right hand ECU. (potentiometer out of range)
    I hooked up diagnostics computer again. 100% pedal is 3.75v, 0% pedal is 0.75v. According to the error code list, they are within range. Moving forward, I replaced gas pedal potentiometer, then replaced both throttle bodies, then cleaned gas pedal potentiometer connectors, then disabled the immobilizer, then replaced both ignition ECUs. Still get to limited to 20% throttle after a dozen miles or so. What's next? Any other possibilities?
     
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  3. virendra

    virendra Karting
    Silver Subscribed

    Jun 14, 2008
    226
    Hong Kong
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    virendra anand
    Have you checked fuel pumps. Over time the pumps in the cars from that era including the 550/360/456 get gunk in the pump as a result of their rubber housing melting into it. Fuel starvation leads to Engines still running but almost choking and it's not something that will show up in diagnostic tests. I would press the valve stem on the Injector rail and have someone crank the engine briefly to see if there is enough fuel pushing through. Another issue common to all these cars is the green ECU station for exhaust even though any issues with that will pop up the Check Engine light
     
  4. voicey

    voicey Formula 3

    Jul 29, 2009
    1,166
    London, UK
    Full Name:
    Aldous Voice
    It's nothing to do with the fuel pumps. You have a wiring fault - either between the pedal and ECU or between the ECU and throttle bodies. Start with the multi-plug behind the RHS seat. There are three and I can't recall which one it is - sorry. But I've seen a bad connection there cause this problem. Also check the connectors at the throttle bodies - they frequently get damaged when removing for maintenance.
     
  5. mahlerfree

    mahlerfree Rookie

    Dec 19, 2019
    41
    behind RHS seat should be around the TCU area, correct?

     
  6. mahlerfree

    mahlerfree Rookie

    Dec 19, 2019
    41
    I wondered what is this relay # 55 "RH Motronic master". Is it a relay for the ECU? Meaning if the relay was stuck open momentarily the ECU could stop working briefly , causing the signals from pedal position potentiometer inop?


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  8. EastMemphis

    EastMemphis Formula Junior
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    May 25, 2019
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    Memphis, TN
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    John
    Did you replace the throttle bodies with new units? I suspect you still have a problem with the throttle bodies as that code is thrown from either the accelerator potentiometer, the throttle bodies or a problem with the ECU. Since your ECU is still working and you've replaced the AP, the two TB's are left as suspect.

    The codes can be thrown because the two TB's are out of spec TO EACH OTHER. That's a key thing here.
     
  9. Qavion

    Qavion F1 Veteran
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    Feb 20, 2015
    5,183
    Sydney
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    Ian Riddell
    Not sure if this applies to the 360, but normally Ferrari engine ECUs have permanent battery power on them, but during start, if the ECU gets "engine turning" signals from the crank sensors, it will activate the master relays which provide additional (ignition key) power to the ECU and to things like fuel pump relay coils, other sensors, etc. I think you would have a lot more problems if this relay failed.
     
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  10. mahlerfree

    mahlerfree Rookie

    Dec 19, 2019
    41
    Not new units, borrowed from a working 360. I suspected it too so I borrowed another set from another 360. No change for both sets.

     
  11. EastMemphis

    EastMemphis Formula Junior
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    May 25, 2019
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    John
    Did you reset the throttle adaptation after changing the TB's? You do this with a two way scanner like an SDX (or in my case, an Autel MS906).
     
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  13. mahlerfree

    mahlerfree Rookie

    Dec 19, 2019
    41
    Yes, with a SD.
    We also test drive the working car with my throttle bodies, without using the SD.
    The working car with my throttle bodies installed does not show any problem after 100miles.
    So that confirmed the problem is not in the throttle bodies.


     
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  14. EastMemphis

    EastMemphis Formula Junior
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    May 25, 2019
    877
    Memphis, TN
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    John
    Since you've done the easy things, the next thing you should look at is your right ECU. Switch the right and left ECU's and see if the problem persists. If it's cleared, then you have your answer and also the solution.
     
  15. mahlerfree

    mahlerfree Rookie

    Dec 19, 2019
    41
    I've replaced them. So , sadly, its not ecu either.

     
  16. EastMemphis

    EastMemphis Formula Junior
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    May 25, 2019
    877
    Memphis, TN
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    John
    Dang! The only thing left is your wiring harness. You've changed everything else.
     
  17. mahlerfree

    mahlerfree Rookie

    Dec 19, 2019
    41
    I even disconnected the immoblizer, fearing that will interfere with something. reflashed ecu of course, using somebody else's ecu. Nothing changes.
    I've replaced the "pedal harness" thats directly connected to the main RHS tunnel harness. Nothing changes.
    That leaves the main RHS tunnel harness that connects to the ECU and TCU. I looked around that harness here and there, for every connector. Nothing damaged, everything factory, seems like nobody ever touched it. How can a harness fail is beyond me.



     
  18. EastMemphis

    EastMemphis Formula Junior
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    May 25, 2019
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    John
    #15 EastMemphis, Dec 8, 2020
    Last edited: Dec 8, 2020
    And yet, that's the only thing left you haven't changed...

    The main harness that connects the TB's to the ECU is probably the issue. I suggest looking in the engine compartment for signs of chafing or heat exposure that might degrade the harness. If you have aftermarket headers without blankets or some sort of serious heat mitigation, it might be the root of the problem.

    This is sort of a hail mary, but if your battery isn't perfect, when you power up the car after a reset, the low voltage may cause the learn to put in the wrong values. The learn happens in the minute after the car is powered after a reset.

    I suggest resetting the car by leaving the battery off overnight (or a couple of hours), then hook up your battery conditioner and turn on the key. The battery minder will keep your voltage in the proper range and the learning cycle may complete correctly. Be sure to wait at least 60 seconds with the key on, then turn the key off for 30 seconds (disconnect the minder), then back on, wait for the OK, then start.
     
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  19. mahlerfree

    mahlerfree Rookie

    Dec 19, 2019
    41
    Now you make me thinking.
    Since I have some random misfire upon cold start, the injection cable going to the ecu is a prime suspect.

    Injectors, coils, throttle bodies, air flow sensors are all on this harness.



     
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  20. 3pedal360

    3pedal360 Rookie

    Jan 11, 2013
    23
    Did you ever solve this? Been chasing my tail for a long time on this exact problem


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  21. mahlerfree

    mahlerfree Rookie

    Dec 19, 2019
    41
    Not yet.
    What have you done to solve this?

     

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