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Strange stuttering while coasting. advice needed please

Discussion in 'A3/S3/Sportback (8P Chassis)' started by bertiebasset, Dec 19, 2012.

  1. bertiebasset
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    bertiebasset New Member

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    [Dec 19, 2012]
    Hi all,

    Fairly new TDI s-line owner here and I'm loving looking through this forum.

    Spotted a potential issue last night and as the title says when coasting in neutral the car runs fine but as soon as I apply a little brake the idle starts jumping around like a miss fire. Anybody had this before or can shed any light on it?

    Cheers all..
    #1
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  3. Geraldy212
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    Geraldy212 Sportback owner

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    [Dec 19, 2012]
    Never had this Bertie, but here is a suggestion. On the TDI, vacuum for the brakes and other needs is supplied from the tandem pump, driven off the inlet camshaft. It is called a tandem pump, since the unit is combined with a fuel pump. Anyway, as far as I know this pump supplies the brake system, but also provides vacuum for the exhaust gas recirculation (EGR) system as well. It may supply vacuum to other engine management devices too. I am sure other members will be along to comment more on this. Anyway, I suggest you might like to get a mechanic to go over all of the vacuum pipes and connections. That is the only definite link I know between the braking system and the engine management. Good luck.
    #2
  4. bertiebasset
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    bertiebasset New Member

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    [Dec 19, 2012]
    thanks for the info Gerald. can anybody else confirm Gerald's thoughts or point me any other direction?
    #3
  5. Geraldy212
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    Geraldy212 Sportback owner

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    [Dec 19, 2012]
    Bertie, I forgot to add, that it would be a good idea to have the car scanned (VCDS) to see if any fault code had been thrown up. If so, that would help to diagnose which area needs looking at.
    #4

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