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348 cutting out

Discussion in 'Technical Q&A' started by Tal, Dec 10, 2003.

  1. Tal

    Tal Rookie

    Nov 5, 2003
    17
    Midlands UK
    Full Name:
    Tal Withington
    Hi All,

    Has anyone else experienced this problem. This has started happening to my car.

    If you start the car and then just let it run. After a while the engine starts hunting and then will eventually die. I've tried blipping the throttle to take the choke off but this revs the car then dies.

    When driving the car the car runs perfect, except on occasions when coming to a halt the engine stops,

    Any ideas?

    Thanks
     
  2. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
    TN
    I don't know exactly what is wrong as the Motronic system is new to me but I would think it might be linked to the engine idling control units. I am not sure how to test them but they are the larger cylinder shapes up toward the front of your engine. I think they are gold/brass in color and are right behind your pressure regulators. I might be wrong but I thought I would try to help out. I just got my 348 and this system is new to me. Please let us know if you find out what it is.
     
  3. 348 Turbo

    348 Turbo Formula 3

    Jul 17, 2002
    1,837
    TAL,
    There is no chole on the 348. Motronic does the fuel enrichment by other means. I'd suspect a TPS, (throttle position sensor), or perhaps the Mass Airflow Sensor. This doesn't sound to me to be a big deal to diagnos for a good fuel injection guy. I'd see if I could run the car by a good fuel injection capable shop and have it diagnosed. I'd bet they find it quick and it's less than $100 fix. Best of luck.
    Jeff
     
  4. Miltonian

    Miltonian F1 Veteran

    Dec 11, 2002
    5,959
    Milton, Wash.
    Full Name:
    Jeff B.
    Hi, Tal: Forgive me a thousand times if you already know this, but have you tried "re-initializing" the Motronic ECU's? It could be very, very simple to fix your problem at no cost!
     
  5. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
    TN
    To reinitialize do you disconnect the positive cable for a few minutes then restart the car and don't touch the gas for 10 mins. or so?
     
  6. bigbaddad

    bigbaddad Karting

    Oct 31, 2003
    135
    Arizona
    Full Name:
    John Roberts
    Yes, exactly.
     
  7. Ingenere

    Ingenere F1 Veteran
    Silver Subscribed Owner

    Dec 11, 2001
    5,904
    On the Limit
    Full Name:
    Dino
    Mine (89 w/2.5) has had this problem occassionally over the last 14 years....only when the AC was running. The fix has always been to clean up the mass air sensor and adjust the idle...and away you go....for another couple of years.

    Ciao...Dino
     
  8. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
    TN
    Thanks.
    Do you clean the inside of the mass air or the connection?
     
  9. Philippe

    Philippe Karting

    Nov 2, 2003
    68
    Brussels, Belgium
    Dino, Where to find the "mass air sensor" ? Thanks.
     
  10. Ingenere

    Ingenere F1 Veteran
    Silver Subscribed Owner

    Dec 11, 2001
    5,904
    On the Limit
    Full Name:
    Dino
    There are 2 of them. One on either side of the airbox. They are between the airbox and the intake plenum. The have an electricl cable attatched to them and they say Bosche and they are black.

    Best of Luck....

    Ciao...Dino
     
  11. rexrcr

    rexrcr Formula 3

    Nov 27, 2002
    1,572
    Kalamazoo, MI
    Full Name:
    Rob Schermerhorn
    Tal,

    Set your idle speed by balancing the two banks. Not difficult if you have a mercury U-tube manometer. Use a tach other than the one in the dash, it's not accurate enough for idle setting (I was spoiled in the dealer network and had an SD1).

    Here's the proceedure in "Parts & Service" section of FC: Setting Idle Speed on Ferrari 348 Motronic 2.7

    Best regards,

    Rob Schermerhorn

    Ps, let us know how it goes :)
     
  12. Tal

    Tal Rookie

    Nov 5, 2003
    17
    Midlands UK
    Full Name:
    Tal Withington
    Thanks Guys I'll give them a try

    Cheers

    Tal
     
  13. Tal

    Tal Rookie

    Nov 5, 2003
    17
    Midlands UK
    Full Name:
    Tal Withington
    Hi All,

    I'm still having the same problem with my car during idle.

    I've cleaned the air mass flow sesor connectors and also the throttle positioning sensor. How do i go about cleaning the sensors inside?

    or is this a no go.

    TIA

    Tal

    p.s An one installed a K+N air filter ?
     
  14. ernie

    ernie Two Time F1 World Champ
    Lifetime Rossa Owner

    Nov 19, 2001
    22,022
    The Brickyard
    Full Name:
    The Bad Guy
    Tal,

    Check your spark plug wires to make sure that they haven't gone bad. Look to see if one of them has burned through. Make sure that all the connections to the coils are clean, and connected properly. You can also check to make sure that the plug attached to the back of the intake cam on the passenger side of the car is clean and plugged in properly. If that gets loose it can mess up the fuel timing.
     
  15. ernie

    ernie Two Time F1 World Champ
    Lifetime Rossa Owner

    Nov 19, 2001
    22,022
    The Brickyard
    Full Name:
    The Bad Guy
    You don't wanna touch the little wire on the inside of the Mass Air Flow Sensor. They are very fine and can break easy. There are two screens on either sides of the MAFS, those can get dirty. To get to the screen you have to remove the air box. Here is what you do:

    1) Loosen the screws on the clamps that are on the intake tube going to the throttle bodies on the side that is attached to the MAFS

    2) Remove the four screws that hold the air box down

    3) Remove the tubes on the back of the air box, that lead to the air intakes

    4) Unplug the MAFS, then Gentley remove the air box with the MAFS still attached

    5) Remove the screws that hold the MAFS to the air box. There are two for each MAFS

    6) Take the MAFS off

    7) remove the clamps that holds the screen on the MAFS. Do this with the screen you want to remove facing down. This way you don't get any dirt on the wire inside the air passage.

    8) clean up the screens then follow the steps backwards to put them back on

    Have fun
     
  16. rexrcr

    rexrcr Formula 3

    Nov 27, 2002
    1,572
    Kalamazoo, MI
    Full Name:
    Rob Schermerhorn
    Have you re-set idle? Do you have error codes and if so, what are they?

    If you're just cleaning contacts you're wasting your time. BTW, hotwire sensor is self-cleaning, shoots high current through it at engine stop. Monitor the input voltage and you'll see the spike when turning the key to off.

    Any car I had with unstable idle I'd immediately connect to SDI to see airflow balance between the banks and look for error codes. Then, hook up the u-tube manometer and reset idle properly. You can do this without SDI. Use an external tachometer, remember to set it as 4 cylinder if you're using Motronic output. The manometer will show you airflow balance. It's an iterative process. It's too easy to set this to blow it off looking for other problems.

    You can check exhaust gas for clues too.

    Let us know how it goes.

    Best regards,

    Rob Schermerhorn

    BTW, only one 348 I couldn't get to idle properly. Upon further diagnosis, it had high cylinder leak percent, and required valve reseating, though not guides (this was a 348 Challenge). Though as these cars age, other issues may occur.
     

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