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Intermittent loss of power (won't clear 2k RPM) and today - a scraping noise :/

Discussion in 'Audi S4/A4/A4 Cab (B7 Chassis)' started by Lafarge, Feb 5, 2014.

  1. Lafarge
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    Lafarge New Member

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    [Feb 5, 2014]
    Hi folks. thanks for reading :/

    Bought my '56 TDiQ 170 a couple of months back, seemed to be a good enough motor until the last week or two. Couple of times it's lost power while driving, both times it's been wet with lots of standing water on the roads - which I avoid if I can - so I don't know if that's relevant. Car has 100k on the clock and has service history, just not all Audi.

    A couple of weeks back, 15 minutes into my commute home, really heavy rain on the M25, loads of spray, it started to lose power - just felt like it had dropped a cylinder, and struggled to get past 2000 RPM unless I absolutely floored it, but even then you could tell something wasn't happy.

    Today, on the M4, an hour into my commute to work it began to lose power, same symptoms, but this time I could worryingly hear a scraping noise coming from the engine bay - at least that's where it sounded like it was coming from - much like the sound of a pad scraping on a disc. Press the clutch, noise goes away, engine revs freely in neutral. Engage a gear, noise is there and increases in volume as you apply engine load with the throttle. Just coming onto the M4 slip from the M25, I thought my exhaust had gone, as it was suddenly really boomy when the revs went from idle to about 1100 - blip the throttle, boom. Really weird :/

    I know it's a long shot, and I know I need to get the fault codes read (presuming there are some). No warning lights, no increase or decrease in temperature, but has anyone else heard or seen these symptoms? The only other thing I've noticed is that when parked, if you turn on full lock, slowly, to manoeuvre in a car park etc, there's a juddering/vibration through all 4 wheels - but it's only momentary as you go from being still, to setting off, so I guess it's just the haldex sorting itself out? Again, maybe (hopefully!!) a red herring.

    Car had an oil and filter change at Audi a month ago, I just fitted a new air and fuel filter, which has dramatically improved the responsiveness and thankfully also upped the MPG a little (as you would expect). I don't thrash it, but I do put my foot down every so often. Always sit at the speed limit or thereabouts, on motorways with cruise engaged. It's had the Audi recall for injectors, but I don't know whether it's all 4, the loom, or what - will call them to find out.

    Any thoughts, very welcome...

    Thanks,

    Rich
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  3. jdp1962
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    jdp1962 Grumpy Old Moderator Staff Member Moderator

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    [Feb 5, 2014]
    Hi,

    Can't help with the engine problem, but the slight juddering you experience when pulling away on full lock is a normal feature of the permanent Torsen-differential (i.e. not Haldex) quattro system fitted to the A4.

    Hope soemone comes along soon to help with the engine problem, which does sound alarming.
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  4. Lafarge
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    Lafarge New Member

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    [Feb 5, 2014]
    Cheers JDP - figured it was just the Quattro doing Quattro stuff, as it never happens at any other time. Grateful to you for confirming it :)
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  5. Lafarge
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    Lafarge New Member

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    [Feb 5, 2014]
    I've managed to borrow an X-Guage code reader so I'll get that connected and post the results.

    Anyone have any thoughts on what could be causing the noise, which stops when I press the clutch? Previously it was just power loss, which cleared after a few minutes, and the car has been fine since (used plenty this weekend with long motorway runs).

    Just took it out at lunch, seemed a little hesitant at first which I thought could just be due to it being cold again. After a ten minute drive to the shops, gave it a shove with my right foot and all seemed perfect. Odd how it's intermittent, which makes me think it's related to the wet weather - but that doesn't explain the noise...

    :/
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