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s3 idling funny

Discussion in 'A3/S3/Sportback (8P Chassis)' started by c6dsy, Nov 27, 2012.

  1. c6dsy
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    c6dsy Member

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    [Nov 27, 2012]
    My s3 started idling weird tonight i drove about 8 miles and then was out car talking to someone then jumped in the turn round and noticed revs dropped down really slow then changing gear was getting backfire once home i took it out of gear and let it idle and its fluctuating between 2000 rpm and just below 1000rpm going up and down and if i rev it there is a back fire too any ideas? Got an ig maxogen fitted and full miltek turbo back exhaust
    #1
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  3. mjr901
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    mjr901 S3 Pollution Plus+ Edition

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    [Nov 27, 2012]
    you could try cleaning the MAF.
    #2
  4. c6dsy
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    c6dsy Member

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    [Nov 27, 2012]
    where is it? and clean it with what?
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  5. MrLapou
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    MrLapou Well-Known Member

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    [Nov 27, 2012]
    Vacuum leak. Oil filler cap seal leak.
    #4
  6. c6dsy
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    c6dsy Member

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    [Nov 27, 2012]

    Cant seem to find any leaks but when I turn it off the circular plastic bit on front of rocker cover hisses away for a bit maybe 15 seconds it has a small hole that is meant to be there that's where air is coming from
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  7. 170sam
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    170sam New Member

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    [Nov 27, 2012]
    PVC valve common fault
    #6
  8. c6dsy
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    c6dsy Member

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    [Nov 27, 2012]

    just replace that then see how it goes?
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  9. 170sam
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    170sam New Member

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    [Nov 27, 2012]
    My bad pcv valve
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  10. 170sam
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    170sam New Member

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    [Nov 27, 2012]
    Yea replace it I'm sure it will fix your issue
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  11. 170sam
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    170sam New Member

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    [Nov 27, 2012]
    Yea just replace it and I'm sure it will fix your issue for you .
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  12. MrLapou
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    MrLapou Well-Known Member

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    [Nov 27, 2012]
    Try taking cover off with engine running to see what happens.
    #11
  13. c6dsy
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    c6dsy Member

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    [Nov 27, 2012]
    if i take oil cap off it runs worse then air hisses out valve at front i will try pcv valve
    #12
  14. jaydav2306
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    jaydav2306 Member

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    [Nov 28, 2012]
    What is a PCV valve and what does it do????
    #13
  15. c6dsy
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    c6dsy Member

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    [Nov 28, 2012]
    Its a valve on the front of rocker cover that takes breathers from block and inlet manifold and has a diaphragm in it to alow them all to breath, seems if diaphragm breaks air leaks straight to inlet causing idle to fluctuate
    #14
  16. jaydav2306
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    jaydav2306 Member

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    [Nov 28, 2012]
    Is this the thing located on the top left hand corner above the oil cap? Good to know
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