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355 2.7 high HC & O2 before cat

Discussion in '348/355' started by Billan, Jan 25, 2010.

  1. Billan

    Billan Rookie

    Aug 15, 2007
    17
    Full Name:
    Mats Billberger
    Checked the exhausts at 45000 km before engine out for belts and found the following values after cat:
    CO 0,07 Right & 0,08 Left
    HC 20 R & 27 L
    CO2 15 R & 14,9 L
    O2 slightly above 3% L & slightly below 3% L
    As the O2 was high, we started to check the values before cat and it shows the right cylinder bank delivers high HC-values, even before and after switching ECU:s and automatic calibration. Also computer check is used and nothing special has showed.
    As next test we are going for a leakdown check and possible engine renewal.
    I wonder if someone has seen this before and have something to add to the list of possible faults?
     
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  3. eric355

    eric355 Formula Junior
    Silver Subscribed

    Nov 30, 2005
    984
    Toulouse (France)
    Full Name:
    Eric DECOUX
    Were the measurements done with the O2 sensors connected or disconnected?
    If they were connected, are they working properly and were the ECUs working in closed loop?
     
  4. Billan

    Billan Rookie

    Aug 15, 2007
    17
    Full Name:
    Mats Billberger
    Eric; Can´t really tell you right now, I will check with the workshop when I talk to them next time. I have just got the figures from the workshop, but I got to ask why you ask the question? Don´t misunderstand me, I´m just curious!
     
  5. eric355

    eric355 Formula Junior
    Silver Subscribed

    Nov 30, 2005
    984
    Toulouse (France)
    Full Name:
    Eric DECOUX
    #4 eric355, Jan 25, 2010
    Last edited: Jan 25, 2010
    I just wanted to try to separate the problems, between an internal combustion problem or an engine management problem.
    A closed loop control by the ECUs with bad O2 sensors can lead to an over-rich mixture. I think that for this basic control it is better, in a first attempt, to run the engine in open loop (without O2 sensors) and thus with the standard fuelling map.
     
  6. Billan

    Billan Rookie

    Aug 15, 2007
    17
    Full Name:
    Mats Billberger
    Thank you for the explanation, I´ll check this with the workshop. My car is in the hands of a very experienced f-man, but he have never seen this before. It looks like he has tried many things, but he haven´t been able to spot the problem yet.
     
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