Weird 360 Modena backfire... | FerrariChat

Weird 360 Modena backfire...

Discussion in 'Technical Q&A' started by MD355, Sep 6, 2015.

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  1. MD355

    MD355 Formula Junior

    Mar 8, 2004
    802
    Athens, Greece
    Full Name:
    MD
    I've had some problems in the past with the timing (messed up by dealer, but fixed with dial gauges based on WSM) and have replaced MAF and Lambda sensors, as well as all intake gaskets (all eight small ones plus the big ones at the top of intake manifold) and of course new spark plugs.

    Now the problem is this : sometimes when engine is not fully warmed up I let the car coast with neutral and the revs drop and as soon as I hit the throttle it pops without the engine revs going up !!! It is irritating because I've had backfire in the past when I release at full revs the gas pedal on the overrun... This now is ridiculous... From low revs I push throttle and "bang" without the engine revs going up... It feels like something is lagging the engine...

    What could it be ? Faulty fuel injector ? Faulty ignition coil ? Faulty ECU ?

    No CEL light whatsoever...

    Also the engine sometimes seems to hunt for idle... Revs drop below 900 and pick up gradually... Something seems to lag...
     
  2. jackgt

    jackgt Formula Junior

    Jan 27, 2015
    574
    california
    Full Name:
    Jack
    There seems to be a lot of THIS particular thing going on with my car also. I would replace ALL of the coils, as there is no way to test them. Before that I would do a ECU reset. I have done it about 10 times and each time a different result!!! Now if I do not hit the gas hard it runs great. I am going to just take it easy, put some miles on it and see what happens. I believe that these ECU's have to LEARN some inputs after the reset. Here is the best ECU reset that I have found.
    Next, start the engine and let it idle for at least 5 mins (Ferrari recommend 4 mins, I prefer to let it idle for about 10). To begin with the engine will sound terrible, as if it’s misfiring. This is because all the trim values have been erased from the ECUs. By allowing the engine to idle the ECU can re-learn the correct trim to be applying to the parameters. The engine note will improve quickly.
    Idle for at least 5 mins from cold. As well as re-learning the adaptive parameters, the ECU also checks that the lambda sensor heater elements are working correctly and tests that the purge valves on theFuel Vapour Emission Control System (aka EVAP) are operating properly.
    Drive the car in 3rd or 4th gear with an engine speed of between 2,000 and 2,500 rpm for 3 1/2 miles (no hard accelerating or erratic shifting). The ECU checks ignition, fuel trim, cat efficiency, lambda sensors, PCV valve operation and EVAP purges.
    Shift to 4th gear and increase engine speed to 4,500 rpm and hold for 30 seconds. This ensure the engine is operating in a steady state.
    Decrease engine speed to 2,000 rpm without changing gear or braking. ECU checks PCV valve operation and EVAP purges.
    Gently stop the car without changing gear, shifting into neutral when required. Let the engine idle for 5 minutes without touching the throttle or changing the engine load (for example by turning on/off any electrical equipment or air conditioning). This allows the ECU to learn the engine idle control properly.
    Switch the engine off and remove the key. Keep the engine off for at least 30 seconds.
    Restart the engine and drive the car normally for 10 minutes (no hard accelerating or erratic shifting). The ECU re-checks ignition, fuel trim, cat efficiency, lambda sensors, PCV valve operation and EVAP purges.
     
  3. Koss2j

    Koss2j Karting

    Jan 9, 2012
    84
    Newcastle Australia
    Full Name:
    Dale Collison
    Hey md355 dif you get to the bottom of the backfire?

    Sent from my SM-N910G using Tapatalk
     
  4. MD355

    MD355 Formula Junior

    Mar 8, 2004
    802
    Athens, Greece
    Full Name:
    MD
    I replaced all 8 coils and I saw no change at all... When i drive the car if I swift to neutral and rev the engine, initially there a hesitation and then there is backfire from the exhaust.. The engine responds as if it there is a lag, combined with rich mixture which backfires and then revs... very weird..
     
  5. 24000rpm

    24000rpm F1 Rookie

    I think u need to use diagnostic tool to see parameters, like fuel trims and timing stuff.
     
  6. Koss2j

    Koss2j Karting

    Jan 9, 2012
    84
    Newcastle Australia
    Full Name:
    Dale Collison
    Hi guys. I have some more news on my backfire. It appears that the fuel cannister and associated valves were bad. I have replaced these and it this stage it appears to have gone with a really beautiful 'on song' exhaust note. True a capristo race exhaust is helping but i dont remember it ever sounding like this and i have owned it for almost 10 years and fitted the capristo immediately back then. The computer threw all 3 codes. Be worth having a look.

    Sent from my SM-N910G using Tapatalk
     
  7. MD355

    MD355 Formula Junior

    Mar 8, 2004
    802
    Athens, Greece
    Full Name:
    MD
    What part number exactly did you replace ??
     
  8. 4redude

    4redude Formula Junior

    Jan 13, 2005
    733
    Fungus Corner
    Full Name:
    Brian Keegan
    The fuel tank vapor valves are predominantly NLA. Change to the new green base gasket
    for the valves and apply some sealant. This may solve your problems . New gasket number is 195049.
     

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