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Thread: 2004 A4 B6 1.8 turbo - Not idling well then revs go up after driving.

  1. #1

    Default 2004 A4 B6 1.8 turbo - Not idling well then revs go up after driving.

    Hi guys.
    I am having trouble with my A4 as my post title suggests.
    On cold start the car idles a bit rough then when a bit warm drives ok
    and then I get the revs going up to 2.5k then down to 800 or so etc.
    My mechanic who I have made quite wealthy since owning the car fixed it before
    with a few new hose clamps as it is apparently a vacuum/breather hose issue.
    The issue has now returned.
    So I am looking at replacing the hoses/tubes at the top back of motor
    where the problem lies or so my mechanic says.
    Has anyone else had the same problem?
    Looking at some videos they also replaced pcv valves and vacuum unit.
    Would like to cover this in one visit back to mechanic so was wondering if
    anyone knew what hoses etc. I should really replace?
    Any help greatly appreciated.
    Last edited by WowdiA4; June 27th, 2019 at 12:03 AM.

  2. #2


    The common failure parts of the vac system are listed in this kit here:

    **Note: You may have some different parts to this kit, I just took a guess based on you having a 2004, and this kit is for most late 2003 and up.

    Visually checking these for any obvious holes/breaks/cracks would be a good start. If they haven't been replaced already I would start with the 3-way hose at the back of the valve cover, the suction jet pump (plastic arrow lookin thing at back of inlet manifold) and the block breather elbow that is under the inlet manifold.

    Hope that is of some help.

  3. #3


    Thanks Matt.
    Yep planned to replace the hoses etc you showed me.
    Will be going for cheaper rubber bits than the ECS stuff though.
    Is that price USD or AUS?
    Kind regards,

  4. #4


    That price was USD. I reckon you could get much cheaper locally.
    Have you scanned the car for codes? You could also check the fuel trims to confirm a vac leak.

  5. #5


    Cheers Matt.
    Yeah pretty sure it's vacuum related.
    Can I check codes ?

  6. Default

    Definitly vacuum check the pancake valve for leaks

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