1991 348tb codes and driveablity | FerrariChat
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1991 348tb codes and driveablity

Discussion in 'Technical Q&A' started by Lucas Picone, Jul 31, 2018.

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  1. Lucas Picone

    Lucas Picone Rookie

    Jul 31, 2018
    12
    Full Name:
    Lucas Picone
    #1 Lucas Picone, Jul 31, 2018
    Hey guy have a costumer with a 91 348, both engine lights are on at idle and while driving the car will stumble aggressively (similar to a misfire) and both engine light will come on and off intermittently, the car does settle on decel but as soon as any throttle is added it jumps and shakes etc.
    I have codes from 1-4 4121, 1211 and I think 1111
    5-8 4121, 1211
    also the speedo only works sometimes, new o2 sensors have been installed. MAFs is good
    tired to clear all codes and let the battery sit disconnected for about an hour. right at start up lights came back on.
    Im thinking it could possibly be a crank sensor/relean. Any body have any info on this?
    Lucas
     
  2. greyboxer

    greyboxer F1 World Champ

    Dec 8, 2004
    12,671
    South East
    Full Name:
    Jimmie
    #2 greyboxer, Aug 1, 2018
    You might want to take a look and/or ask in the 348 section
     
  3. steved033

    steved033 F1 World Champ
    Owner Silver Subscribed

    Apr 12, 2017
    10,114
    Atlanta, GA
    Full Name:
    Steve D.
    #3 steved033, Aug 1, 2018
    Found elsewhere, not sure of accuracy. If what below is accurate, I'd clean the mass air flows.

    Hot wire air flow meter 1111
    Engine coolant temp sensor 1112
    Throttle potentiometer 1113
    Lambda sensor 1114
    Lambda regulation Additive value for self adaption 1211
    Lambda regulation multiplicative value for self adaption 1212
    Lambda regulation intake manifold compensation 1212
    Valve 4111
    Injection valve 1 1411
    Injection valve 2 1413
    Injection valve 3 1414
    Injection valve 4 1412
    RPM sensor 1121
    Stroke sensor 4112
    Power module not used 4113
    Battery voltage 1122
    TDC control unit recognition 4114
    Secondary air solenoid valve 1123
    Purge valve 1124
    Catalyzer temp ECU 4121
    Catalyzer temp to high 4122
    Speedometer signal 4123
    Short circuit on idle regulator 1311
    Open circuit on idle regulator 1312
    No error detected 4444
    M.I.L. 1444
    Electronic control unit 1313
    Compressor connection signal 4131

    sjd
     
  4. ernie

    ernie Two Time F1 World Champ
    Lifetime Rossa Owner

    Nov 19, 2001
    22,614
    The Brickyard
    Full Name:
    The Bad Guy
    #4 ernie, Aug 1, 2018
    Last edited: Aug 1, 2018
    4121 is for the catalytic converter temperature control unit (aka: Cat TCU) and/or the catalytic converter thermocouple.
    If the Cat TCU/s is/are disconnected the Montronic ECU will store a silent code. The Motronic ECU will also store the code if it is not getting a proper signal from the Cat TCU. Meaning that either the Cat TCU is faulty, and/or the thermocouple is faulty. So check to see if the Cat TCUs are connected. Also if they are disconnected it will have no affect on how the car runs. I have had the Cat TCUs complete removed from my car for many, many years and it does not affect how the engine runs.

    1211 is lambda regulation. That often is a faulty O2 sensor/s. I have swapped the O2 sensors from one side to the other, to check and see if the code jumps sides and appears on the other bank of cylinders. But it could be related to the issue with the MAFS not allowing the Motronic to adjust the air/fuel ratio properly during closed loop operation.

    1111 is the mass air flow sensor. Before replacing the MAFS check to make sure that it is clean on the inside. There have been times the person is running a K&N air filter and the oil contaminates the MAFS. Also, make sure that the resistance between pins 1 & 5 is set to 383Ω.

    I would also check the condition of the spark plug wires, to make sure they don't have a short.
     
    bayferrari likes this.
  5. Surfari

    Surfari Karting

    Nov 4, 2016
    149
    Redondo Beach
    Full Name:
    Luke
    #5 Surfari, Aug 1, 2018
    I have a 1211 or 1212 (depending on the day) ONLY at startup. The car runs and drives great, and the code doesn't pop back up while driving. My theory is that the coolant sensor is bad and telling the ECU to go into close loop while the car is warming up (and running rich), thus maxing out the Lambda adjustment. I'm going to replace the sensors next week (and clean some connections) and see if that makes a difference.

    You might have a similar issue going on since you are getting both at startup. Other than that, replace the crank sensors. That fixed a few similar problems I was having.
     

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