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Excessive vacuum in crank case?

Discussion in 'A3/S3/Sportback (8P Chassis)' started by Minstadave, Nov 29, 2012.

  1. Minstadave
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    Minstadave Member

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    [Nov 29, 2012]
    I've been getting awful MPG recently and have noticed that if I remove my oil filter cap whilst idling the cap is hard to remove, once I get it off the engine is sucking air in via the oil filter cap and the revs rise.

    Is this normal? I think I may have a knackered PCV valve. Is it a DIY replacement job?
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  3. Minstadave
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    Minstadave Member

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    [Nov 30, 2012]
    Anyone know if it's normal for the 2.0T to suck air through the dipstick and oil cap at idle?
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  4. OVRA3
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    OVRA3 Well-Known Member

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    [Nov 30, 2012]
    If I take mine off or pull the dip stick I the car runns rough and tries to stall... Is that what you mean?
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  5. MrLapou
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    MrLapou Well-Known Member

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    [Nov 30, 2012]
    sounds normal to me with filler cap off.
    Last edited: Nov 30, 2012
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  6. Minstadave
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    Minstadave Member

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    [Nov 30, 2012]
    When I take the oil cap or dipstick out it starts sucking loads of air in and the revs rise. It's meant to run rough normally.
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  7. OVRA3
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    OVRA3 Well-Known Member

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    [Nov 30, 2012]
    Dont think so mate, when you take off the cap it should shudder and struggle... Sure someone who knows more will be along soon
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  8. RobinA3
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    RobinA3 Well-Known Member

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    [Dec 3, 2012]
    Yes there should be a vacuum inside the engine. The crankcase pressure should always be negative so when you remove the filler cap or dipstick when the engine running it will run like a sack of **** as unmetered air (air which is not measured by the airflow meter) is entering the engine.
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  9. wuta3
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    wuta3 Well-Known Member

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    [Dec 4, 2012]
    I had a rough idle, with reeealllyyy hard to remove oil cap etc and it was the PCV. It's an easy job on your drive. I gave the tubes a good clean too because they were caked in ****.
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  10. becks2012
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    becks2012 New Member

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    [Dec 4, 2012]
    Yes you require a new PCV valve the oil filler cap should not be that difficult to remove when engine on idle 5 min job
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