Need help to diagnose Mercedes Benz 2012 SLS AMG
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  1. #1
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    AvechuchoAxel's Avatar
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    Default Need help to diagnose Mercedes Benz 2012 SLS AMG

    This vehicle had a lot of problems with wires. I found some wires chewed up by rodents.. You can imagine what came next.....
    2012 SLS AMG M159.980 A/T

    Frustrating and sad story short:
    Vehicle have misfire on cyl #7 while idling. after 2300 or 3000 rpm all the faults goes away.
    Spark plugs: REPLACED (8)
    INJECTORS: REPLACED (8)
    Coils : REPLACED (8)
    No improvements or changes whatsoever...

    After finding chewed wires and looking closely every single inch of the engine harness a new one was ordered out of the dealer.

    Engine Harness: REPLACED

    Looking at Lambda values while idling I found UPSTREAM LEFT SIDE
    o2 sensor not working. So I ordered a new one.
    While replacing the old
    O2 sensor I found on left side that upstream was wrongly installed on DOWNSTREAM position. So I change positions and replaced the upstream 02s anyways..

    Customer tell me that the ECU was replaced by dealer, so I run a follow up after ME replacement.

    No big changes on the CYL #7 misfire.
    After checking LIVE DATA - FAULT COUNTER cyl#7 shows misfires at idling engine speed, but revving above 2600 RPM all the faults counts goes to 0.

    COMPRESSION TEST SHOWS NORMAL VALUES

    So, I eliminate fails from Coils, Spark plugs, Injector,
    wire harness, 02S.
    What else do you guys recommend to look at it?

    Find attached 2 short videos. AFTER 02sensor replaced.
    Attached Files Attached Files
    Last edited by AvechuchoAxel; 3rd June, 2020 at 07:53 PM.

  2. #2
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    Default

    I took screen pictures this afternoon. There is a particular one (#6) where it shows cylinder number #7 of scale.

  3. #3
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    Default more pics

    I can't attach all at once...... ( i think..)

 

 

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