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Hiss on cold start up??

Discussion in 'A3/S3 Forum (8L Chassis)' started by walla, Jan 29, 2012.

  1. walla
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    walla New Member

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    [Jan 29, 2012]
    Hi guys, i've got a a3 quattro and ive noticed something strange with my car. When starting up the car cold it'l rev at 1,200 rpm for a few minutes and then settle slowly down to about 800rpm. Now not sure if this is normal but it's always been like that.

    However now ive noticed that just before it starts to drop there a very distinctive hiss. Is this normal??
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  3. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Jan 29, 2012]
    Revs will always be higher on cold start and they will drop as the engine warms but yours might be a bit high.

    If I was you I'd stick your head under the bonnet and see if you can pin point the hiss as it sounds like you might have a split hose somewhere.
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  4. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Jan 29, 2012]
    Its most likely the SAI... if its hissing then it could be that the vacuum pipe has been disconected... yours had an N249 bypass or something?

    <tuffty/>
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  5. Dani_B19
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    Dani_B19 Audi-sports own special child.

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    [Jan 29, 2012]
    Do you have the aircon on when starting up? If my air cons on when i first start the car, you get a whining/hissing noise.
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  6. walla
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    walla New Member

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    [Jan 29, 2012]
    Just stuck my head under the bonnet (luckily its cold outside so it didnt take long for the engine to get cold)

    Theres definitely a small click before the hiss, almost like a switch clicking by the battery. The hiss it self is coming from the front of the car below the throttle body. Not sure if it makes a difference but i have the Electronic throttle on mine.
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  7. Y83OLK
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    Y83OLK Hulk Smash!

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    [Jan 29, 2012]
    Sound like the a/c fan.. see if it does it with the climate set to Econ.
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  8. walla
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    walla New Member

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    [Jan 29, 2012]
    The air conditioning/heater was off at the time.
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  9. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Jan 29, 2012]
    SAI....

    <tuffty/>
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  10. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Jan 29, 2012]
    ...or a vacuum leak from the PCV...

    <tuffty/>
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  11. walla
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    walla New Member

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    [Jan 29, 2012]
    any ideas on repairs costs etc.

    and how it would affect my cars performance
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  12. QuattroRich
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    QuattroRich Quattro Formaggio

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    [Jan 31, 2012]
    I have an A3 quattro and have this hissing sound coming from the same place. Only seems to have come about now the cold weather has set in and disappears once the engine has warmed up after a couple of minutes.

    Can this problem be solved easily?

    Thanks
    #11
  13. Reesy
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    Reesy Well-Known Member VCDS Map User

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    [Jan 31, 2012]
    It's the SAI as tuffty said. My 2 tqs' have both done/do this...
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  14. QuattroRich
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    QuattroRich Quattro Formaggio

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    [Jan 31, 2012]
    Cheers Reesy, will look into it
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  15. Reesy
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    Reesy Well-Known Member VCDS Map User

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    [Jan 31, 2012]
    Shouldn't need to mate, if it makes a noise and then cuts off as the revs drop, its more then likely working fine. Mainly happens when car and ambient temp are cold.
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  16. QuattroRich
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    QuattroRich Quattro Formaggio

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    [Jan 31, 2012]
    I was hoping that it was just due to outside temp. Cheers fella
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