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PCV valve TFSI

Discussion in 'Audi S4/A4/A4 Cab (B7 Chassis)' started by twist123, Oct 19, 2012.

  1. twist123
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    twist123 Member

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    Hi Guys,


    Need some help with a diagnosis, Im finding Im having a problem with oil consumption with my A6 TFSI (BPJ). I understand this is the A4 section but there are more A4 owners than A6 owners with this engine so hopefully you guys can help out.

    I have a feeling the PCV could be part of if not the cause, but do realise these drink oil due to design. Just need to check a few things as theres conflicting info elsewhere. Car runs beautifully and pulls hard when turbo kicks in with no smoke.

    When cars started if I remove the dipstick briefly I hear a hissing sound. With car started I open the oil cap (dipstick in) and as I lift the cap I can feel quite a strong vacuum at idle.

    Is this sign of failure or correct?

    Does anyone know if the silver crank breather pipe has a check valve in it like the MKV GTi?

    Thanks in advance
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  2. murran
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    murran Active Member

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    should be no more difficult to remove the oil cap when its ticking over to when the engines off. shouldnt be able to "feel" vacuum at the cap as the crankcase shouldnt be under vacuum!

    removing the cap should unbalance the idle. but if it struggles to maintain tickover then its deffo faulty!
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  3. murran
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    murran Active Member

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  4. twist123
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    twist123 Member

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    Hi Murran,

    Thanks for the posts, no issues with idle or performance, I believe the puck has 3 valves in it, when we bought the car it had erratic idle the dealer "replaced" the PCV and codes cleared and idle returned to normal, just wondering if they shouldve replaced not only the puck but the hoses and breather line also as Im thinking that may be part of the ongoing issue.

    Definitely a vacuum at idle from the oil cap pulling it downwards so some part of the PCV must be knackered, should probably just replace the lot with all hoses etc.

    If one of you ladies or gents could please check if you have vacuum just for final confirmation for me Id really appreciate it.

    Thanks all
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  5. twist123
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    twist123 Member

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    Part replaced, still some vacuum, Im guessing this is normal. Will replace silver breather as a matter of maintenance and switch oil from edge to something else.
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  6. GarJE
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    GarJE Member

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    You should have a vacuum at the filler cap. The cam case is being depressurised by the draw from the inlet tract. The pcv valve is there to divert vacuum fore/aft of the turbo when on/off throttle. Failure of the pcv would cause pressurised turbo air into the cam case, forcing oil out of the filler cap.
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  7. twist123
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    twist123 Member

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    Thanks for tge confirmation and the detailed post, kinda figured that after much reading but great to have confirmation. 35 quid spent but guessing ill need a spare anyway at the rate these are supposed to go.
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  8. murran
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    murran Active Member

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    if the crankcase is under vacuum then the inlet is drawing in unmetered air from it. undoubtedly causing the idle problems you have.

    if you totally blank off the plastic hose to the inlet manifold does it tickover any better?
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  9. twist123
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    twist123 Member

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    Hi murran, the idling is fine, no issues with idle or performance.

    From what I understand GarJe diagnosis is correct as when the PCV valve fails it throws oil around the cap and coil packs along with erratic idle, I am experiencing none of those symptoms, Im also not pulling any codes.
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  10. murran
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    murran Active Member

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    these tfsi units do use oil. some worse than others. audi say a certain amount is normal. in my mind using more than a litre in 2000 miles isnt normal.

    how much is yours using?
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  11. twist123
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    twist123 Member

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    About 250ml-300ml every 500 miles, depending on driving, a lot of stop start, cold driving it will use more. Supposedly up to 1L to 1000km is considered normal by Audi. Ive heard of people switching oil and the situation improving, currently using Edge 5-30 so may switch to Fuchs Titan 5-40 after a Seafoam.
    Last edited: Oct 23, 2012
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