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S3 losing power/ not boosting

Discussion in 'A3/S3 Forum (8L Chassis)' started by fluffsri, Mar 14, 2011.

  1. doughty29

    doughty29 Member

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    i had a simular problem on mine, it turned out to be a blown fuse, the breather pipe under the inlet manifold was popping open under presure and was pushing back on when not under pressure.
     
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  3. blued

    blued Member

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    I fitted a new valve today, the one that sits on top of the cam cover and has 3 hoses connected to it and an electrical plug - is this the N75 or is the N75 valve the one on the airbox pipe that has 2 pipes, one going to the actuator? I am now back to where I was when I first started having problems. The car will boost and hold 15 PSI and then it will just completely drop off. Then it will boost to just 4 PSI, if I back off sometimes it will boost to 15 PSI again. It makes no difference if I disconnect the plug on the valve.

    With the old valve 95% of the time the car will only boost to 4 PSI. Rarely mid journey it will boost to 15 PSI again when accelerating but it hasn't had full boost when initially starting the car for probably a month now.

    So changing the valve improves things but does not resolve the problem. I'm worried that if I run it like this with the new valve it will end up like the old valve. If the valve I have replaced is not actually the N75 then can someone tell me what it is and what it does? I put the old one back on an straight away only 4 PSI.
     
  4. blued

    blued Member

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  5. blued

    blued Member

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    Sorry just saw this, I've checked the breather that is under the middle of the inlet manifold and it is secure. The vacuum hoses at the left hand side seem to be good as well.
     
  6. doughty29

    doughty29 Member

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    The part that was faulty was a breather pipe that had a push in style clip that would pop open under boost, could be a collapsed pipe, looks fine from the out side, but the inside collapses under pressure?
     
  7. blued

    blued Member

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    OK I found the problem, when I went to change the N75 valve it fell apart! I fitted a new valve today and now it holds boost but only boosts to 10 PSI max. I believe standard is 15 PSI? Do I need to adjust the actuator arm to increase the boost? I remember having to do that with my old Cavalier Turbo.

    Also the part number on my old sensor was 058906283, the new one is 06A906283E. Is this a modified/replacement part or could this be the reason the boost is low?

    Edit: Looks like the part number did indeed change - N75 boost valve, standard 058F original version VAG Products German Auto Spares - suppliers of VAG Febi Car Spare Parts
     
  8. badger5

    badger5 www.badger5.co.uk
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    you should not need to adjust actuator no.. is n75 plumbed in correctly?
    n75 electrically off will confirm wastegate pressure (5psi the norm)
     
  9. blued

    blued Member

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    Pretty sure it is plumbed in properly, longest tube from the N75 goes in the air box pipe? By electrically off do you mean unplug it and then when I drive I should get 5 PSI?
     

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