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2.5 TDi down on power

Discussion in 'A6/S6/Allroad forum (C5 Chassis)' started by BX Bandit, Jul 19, 2013.

  1. BX Bandit
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    BX Bandit New Member

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    [Jul 19, 2013]
    Hi Everyone,

    A year ago, I made the break from Citroens (my last and indeed the turning point, being a 51 plate C5).
    Anyway, after driving a mates A6 2.5 TDi 155 bhp, I decided a V6 diesel was for me and I proudly bought an Allroad 2.5 TDi 180 BHP with manual, Bose and the fancy twin spoke wheels.

    I have today replaced the nearside front suspension airbag and the brake light switch and all is well.

    However, what I have been noticing over the last week or so, is the lack of power up to 3000 rpm. OK, I don't expect too much up to 1500 rpm, but I used to notice a gradual increase in torque till 2000 rpm and then a little surge of torque and a slight change in engine note which would give a smooth and good response until 3000 when the turbo comes in.

    That increase from 1500 up to the 3000 is distinctly lacking. At 3000 the turbo comes in as always and power is as usual.

    Does anyone know what gives this small but noticeable surge of power around 2000 rpm? Variable valve timing? VAriable vane turbo? I've had a casual look of the vac circuit and can't see anything untoward.

    As an extra bit of info, on my last but one drive the car just wouldn't go above 2500 ish, foot down in 3rd or 4th but refusing to climb the revs (this was up a small incline). This reminded me of my mates Audi that used to do a similar thing when the catylitic converter failed. However, I just went out for a spin and aside from the lack of power until the turbo kicks in, it managed to climb the rev range to 4500.

    So, what are the symptoms of cat failure? and is it intermittent?
    #1
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  3. gen.heinz guderian
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    gen.heinz guderian Well-Known Member Regional Rep VCDS Map User

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    [Jul 19, 2013]
    Hi and welcome , best thing to do is get it scanned with VCDS. Might help to pinpoint any problems the car has.
    #2
  4. BX Bandit
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    BX Bandit New Member

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    [Jul 26, 2013]

    Hi, thanks for replying and apologies for a delayed reply.


    my mate assured me it needed a new maff, despite the vcds listing a manifold pressure symptom. A new maff made no difference, but by chance I noticed a small plastic spigot in the vac circuit was at an angle and actually broken. Long story short is that the tiny leak in the vac circuit is now cured a the problem and if anything, the car has never performed better, a good hard pull from 2500 rpm whereas it used to be much more linear until 3000 and then the turbo would kick in.

    so, performance wise, I'm happy with the car.

    however, a do have the fault code 01375 38-10. A common fault code related to the front hydro mounts with electrical connections. For some reason my mate advised me that it was the near side that needed replacing. I did this yesterday but without any improvement in the vibration at tick over and the fault code still exists.

    having read about on the various forums, it seems the obvious sign of failure on these mounts is the release of a red silicone based fluid(oil?).
    the problem is, neither of my original mounts show any signs of fluid leakage.

    so, my questions are:
    1) does the 38-10 part of the code signify which side of mount has failed?
    2) have they been known to fail electrically rather than hydraulically?
    3) is there any way of testing a mount with a multi meter? If so, are there any known values?
    3) the only other way in which the car could register these faults if faulty wiring on the car itself? Is there any known problems in this regard?
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  5. adamss24
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    adamss24 Well-Known Member

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    [Aug 1, 2013]
    Hi, is the vibration excessive at idle? Manual or auto ? In some cases the dual mass flywheel can give a vibration at idle or a worn injector. I too have the above fault code but- in my case- it's caused by slight vibration from the dual mass flywheel as my car is high mileage and been used loads for towing. The mounts leak as well and they do leave marks on the mounts, it looks like dry water marks if you know what i mean... One thing to bear in mind, genuine mounts are expensive and they don't last, replaced a pair on a friend's allroad and that only lasted 2k ! Tps did not want to hear about the failure...
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  6. BX Bandit
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    BX Bandit New Member

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    [Jun 28, 2014]
    You were indeed correct Adamss24. I have just last week got the dmf and clutch replaced. It's like a new car! The engine is supremely smooth and seems happier to pull. It even seems quieter. Gear change is massively improved as the eccentricity of the dmf was 'dragging' the clutch and making gear changes extremely slow, crunchy and indeed painful!

    Of course, there can not be complete satisfaction!

    The car has always made some odd grumbling noises at low speed and on full lock.
    Slightly more worryingly, it would make a thumping or throbbing bumping sound/vibration, heard and felt through the car as a whole and through the seats. This would by be a rhythmic thump, approx once per second at 5 mph, so, at a guess one thump per revolution of the wheel. This would be more pronounced up an incline I.e, under torque.
    The problem has worsened in that it now thumps under acceleration, in any gear (although the lower the gear, the greater the torque, the greater the thumping) and will do so at motorway speeds. Further, it doesn't do this when cold, it won't make a sound for at least 15 minutes from cold. I can only assume diff or gearbox oil is heating up and causing the problem.
    The noise comes from the back of the car which points to the rear axle/diff. I have been advised that there is a viscous coupling I. The rear diff which clearly once warm isn't performing correctly.
    Can anyone please advise what I should do? My funds have all but been exhausted on the dmf and clutch......
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  7. adamss24
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    adamss24 Well-Known Member

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    [Jun 30, 2014]
    If the car had a towbar and abused in it's life then the play is in the rear diff. Unfortunately there's no really cure unless you fit a new one or get one rebuilt, however setting the backlash on the diff bearings is rather complicated and require pulling the bearings off many times which will damage the bearings if proper tools are not used ! I would live with it if i were you or go for a 2nd hand good unit to swap !
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  8. BX Bandit
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    BX Bandit New Member

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    [Jul 6, 2014]
    Hi Adamss24,

    There was no tow bar on it when I bought it nor anything to suggest one had been fitted/removed when I fitted mine.
    It's not really 'liveable with'. It's not pleasant to drive and I do worry about breaking down somewhere.
    I'm going to start a new thread with an appropriate title.
    #7
  9. adamss24
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    adamss24 Well-Known Member

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    [Jul 6, 2014]
    Every allroad i came across had a factory fitted towbar, even one i had with a low range gearbox had a factory fitted towbar but the socket wasn't wired in- towbar was fitted though !
    #8

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