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Uneven idle 2004 8P

SR71 Mar 20, 2009

  1. SR71

    SR71 New Member

    I have a problem with a slightly uneven idle on my wife's 2004 A3 8P 2.0 TDi.

    There are obviously various threads on this great forum with information about what might be the reason for this situation, however...

    I have VAGCOM'ed the car and there are no faults although the DIS does sporadially illuminate the low coolant amber light on start-up. The car has not lost any fluid though in 2.5 years so I suspect the coolant reservoir sensor is a little dodgy. The light goes out of its own accord after about 2 mins of driving.

    I guess the sensor might be causing the problem, but I'm inclining towards chasing up another possibility first.

    My hunch is that the EGR system is at fault.

    The idle hunts between about 780-850rpm and the associated air flow in g/sec illustrates the same tendency.

    I really know nothing about the A3 and its EGR cycle, but flicking through the measuring blocks with VAGCOM I can see that there is a discrepancy between demanded and achieved EGR flow? Is that the right terminology?
    Maybe the EGR valve is on the way out, or rather, after 82K miles, is blocked up.

    I'd like to ditch the EGR and have seen various blanking plates (Allard? Jabbasport?) but it seems Allard are out of business? Can someone
    point me in the right direction of a full system i.e., a blanking plate, catch-can etc etc?

    In addition, if I'm going to change out the EGR it really seems pointless not to clean the inlet at the same time - although of course, the EGR seems a relatively easy job, whereas getting behind the block to get the inlet out seems much more involved...

    However, try as I might, I have not been able to locate a "How to" for this on the 8P A3?

    I have installed Elsawin v3.4 but would you believe it, it says nothing about how to remove the inlet manifold!

    Similarly, the Haynes manual only goes to 2003 and although various WWW pages detail the process for a Jetta TDi, but nothing for the 8P!


    Can anyone shed any light on the issue? I'd like to know if its easy enough to do at home?

    Many thanks for any help.

    Great forum.
  2. sprout99

    sprout99 Member

    it is typically fluttery

    Check the EGR isn't leaking, the turbo pipes to and from intercooler can split
    and also consider getting idel speed increased

    Factory setting is about 800rpm we had ours turned up to 900 as it would randomly cut out when it had been sat in sun all day, cold engine and aircon used ???

  3. Crunch

    Crunch Member

    Mine does the same mate, makes the car judder a bit and sounds **** from outside. Not had time to chase the fault yet though.
  4. SR71

    SR71 New Member

    Just a quick update on the car.

    After umming and ahhing about whether I could get the manifold and EGR valve off myself at home, I bailed on the idea and let my local Audi specialist at it.

    I reckoned first port of call in sourcing the reason for the problem was to clean out and/or replace the EGR and whilst at it, clean out the manifold from any of the gunk that might have accumulated over 83K miles.

    Car has come back from the specialist and none of the symptoms are there any longer. They told me the EGR was working fine (so it was merely cleaned and re-fitted), but that there was substantial deposition in the manifold.


    Just to repeat, the symptoms were an annoying vibration through the car at idle. It would not manifest itself on start up from cold though. It was only as the car became warm, that the issue became apparent. I would not quite call the vibration "significant" but it was annoying. The rpms would not really hunt, although every now and again they'd dip between the previously mentioned ranges, but the associated sound was quite uneven.

    I was initially worried the symptoms might mean issues with the clutch/gearbox, but the above didn't make sense were that to be the case. They'd be there regardless of the operating temperature of the engine if so surely?

    I discovered that it was less obvious when "D" was engaged, but certainly, at the lights, if you dropped the car back into "N" or "P" it was noticeable.

    If you looked at the actual engine whilst in either of these slections, it really was moving around on its mounts.

    HTH for anyone with similar symptoms.
  5. Crunch

    Crunch Member

    Sounds, EXACTLY like mine mate. I need to clean mine out, how long does it take?
  6. Lee_R

    Lee_R Active Member

    Snap, mine has these exact symptons, starting to bother me too but didnt think it was anything too bad so have left it. Might take it to my local place and get them to clean it for me. Thanks!
  7. SR71

    SR71 New Member

    My garage charged me ~£70 for the work so not more than 2 hrs at their rates I'd imagine...but then I am a good customer.

    Unfortunately, I didn't ask them to take some pictures...

    Obviously pleased it was nothing more sinister.

    The car has been otherwise faultless although the manifold flap motor was replaced under warranty a while ago.

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