Mini R50 Misfire Diagnosis using INPA

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  1. Mini R50 Misfire Diagnosis using INPA 
    #1
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    anglo-nubian's Car Details
    Model of Car:
    R50 Cooper
    Year of Manufacture:
    2005
    Transmission Type:
    Man
    Car Body Type:
    Hatch

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    Hi All,

    I see from looking around here that the clientele are almost exclusively RWD, but very knowledgable, hence my decision to post here......

    My wife's recently aquired an '05 R50 Cooper, but as I've become more familiar with the car I've realised that there's a subtle misfire going on.

    I'm new to INPA, but I've had a look at the analogue readouts with the car in motion and strangely, the 'roughness' values remain quite firmly rooted to zero under load, rising a little on the over-run or at idle.

    Knock sensor voltage seems quite erratic, jumping up and down all over the place (but perhaps that's normal ?) which made me suspect a faulty sensor, but disconnecting the sensor seemed to exacerbate the existing problem rather than a) curing it or b) creating a totally different one. - Interesting ?

    I'm not getting any fault codes, I've already changed plugs & leads but I'd like a firm diagnosis before I fire more parts at it (coilpack next)

    I'm thinking that perhaps erratic ignition, sensed by the knock sensor is being 'smoothed over ' by the ECU retarding timing to achieve quieter running, therefore when I disconnect the knock sensor, the 'smoothing' is removed and I get to feel the misfire in it's raw state.

    Does any of this make sense, or am I doing the old 2+2 = 37 routine ?

    Thanks,

    Glenn.
     
     

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    #2
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    TheEnd's Car Details
    Model of Car:
    540
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    1998
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    Auto
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    Saloon
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    It's possible.
    The rough running only works at idle speeds, so you'll often see it freeze when revved up a little so that isn't much use.

    The knock sensor is a piezo electric microphone which listens to the noise of the engine block. The faster and greater load it is under, the more noise it makes. There are tables inside that will have expected noise levels, and the ECU is looking for any spikes that are above this, and when that happens, it will retard the ignition timing by something like 2-3 degrees and see if that quietens things down.

    In your case, you only have one sensor, so maybe trying a new one could help rule that out.
    RealOEM.com * BMW R50 Cooper Engine Block Mounting Parts
    The majority of 6cyl engines have two, so swapping them could have been an option.

    If that doesn't work, you can also try using a higher octane fuel and see if that helps.
     
     

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    #3
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    goldbcfc's Car Details
    Model of Car:
    Z4
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    2003
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    manual
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    roadster
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    I always thought misfiring was down to poor coil packs and spark plugs wouldnt changing them fix the problem?

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    #4
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    TheEnd's Car Details
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    True, that would be for a proper misfire, but I would have expected one of those to show a fault code somewhere.
    What might be happening is a power reduction similar to when traction control kicks in. The ECU usually does the same thing and retards the timing cutting down on the power produced to help avoid wheelspin.
     
     

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