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Very low boost??

Discussion in 'A3/S3 Forum (8L Chassis)' started by Speedy Steve, Aug 31, 2009.

  1. Speedy Steve
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    Speedy Steve Active Member

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    [Aug 31, 2009]
    Ok guys im having some boost problems i can feel the turbo spool up and hear it but just have no power. I cant hear any boost leaking but lastnight i think i hit limp mode as the car just feels so soft after 3000rpm is there anyway of preasure testing the boost system easyly or am i better off spending the time looking through all the hoses or taking it to some one?
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  3. A3Tom
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    A3Tom Smell my finger.

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    [Aug 31, 2009]
    I'd have a good nose around all the hoses etc firstly, could have a split or a clip thats broken off. Start with the simple (cheap!) things and take it from there.

    T
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  4. Speedy Steve
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    Speedy Steve Active Member

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    [Aug 31, 2009]
    Ive be having a look at the hoses cant seam to find anything one question though is what is the plastic box with a vacume hose to it on top of the rocker cover doesnt seam to be connected to anything other than one vacume hose. Can i disconnect the hoses from the throttle body and form the alloy pipe that comes round the side of the engine and preasure test that without causing any crank case preasure problems?
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  5. Speedy Steve
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    Speedy Steve Active Member

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    [Aug 31, 2009]
    Ok ive tested the intrercoolers and they are fine went up to about 25psi with no sign of any leaks. the hunt goes on!!!
    Last edited: Aug 31, 2009
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  6. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [Aug 31, 2009]
    Well with the boost leak test sounding good, i do not suppose you have an N75J valve on there do you?

    Also have you tried clearing/reading the codes to see what triggered limp mode? As she may stay in limp till the code is cleared
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  7. Speedy Steve
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    Speedy Steve Active Member

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    [Aug 31, 2009]
    Ive found the hose going into the rocker cover was loose infact it was so loose i could nearly pull it off. then i noticed the small vacume hose thst goes to the plastic box ontop of the rocker cover wasnt in all the way not sure if either of these would cause the limp mode or lose of boost.
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  8. b16 will
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    b16 will Member

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    [Aug 31, 2009]
    MAF can give the same symptoms...
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  9. Speedy Steve
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    Speedy Steve Active Member

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    [Aug 31, 2009]
    the car was standard as far as i know when i bought it and all ive fitted is a Forge diverter valve and Miltek exhaust which have both been on a while so i dont think i have a n75J on it.How can i tell
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  10. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [Aug 31, 2009]
    If you havn't changed it then you probably don't have. Have you read the codes?
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  11. Speedy Steve
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    Speedy Steve Active Member

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    [Sep 2, 2009]
    Well after having the battery disconnected on monday working on the car it ran on boost although a little hesitent and slugish was felt like i was gtting more boost but after a while it went back to limp mode. I have purchased a cheap ebay Vagcom lead to just try (i will when funds allow buy a propper one) so hopefully will be able to read the errors soon.

    I have only preasure tested the hoses going to the intercoolers and the intercolers them selves, none of the vacume hoses have been checked. to fully test it i guess i have to block the hose to the rocker cover, the hose off the turbo and each end of the turbo inlet pipe. Are there any others i should block before doing a full preasure test?
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  12. Speedy Steve
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    Speedy Steve Active Member

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    [Sep 7, 2009]
    Found 2 leaking hoses in the breather system have ordered new ones and hope it will solve all my problems
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  13. steviet
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    steviet Member

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    [Sep 7, 2009]
    Steve how did you test the intercooler hoses mate?.
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  14. Speedy Steve
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    Speedy Steve Active Member

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    [Sep 8, 2009]
    I took the charge pipe of the turbo end unclamped it, disconnected the pipe to the n75 and blocked it off the disconnected the hose from the recirculating valve and put a compressor connector in that hose then took the inlet manifold hose off and connected it to the charge pipe. Then connected the compressor well the pipes were firm (20 psi) i watched the gauge to see if the preasure dropped if it did i knew there was a leak! This doesnt check any of the vacume or breather pipes though. Dont forget to disconnect the battery - lead!
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  15. s3_kev
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    s3_kev Stage2'd!!!!!!

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    [Sep 8, 2009]
    if you read your other thread on boost pressure testing your find i replyed saying just to pressure test from the hose at the charge pipe no need to block anything off after there as then you will be eliminating all hoses pipes etc on the boost side of things, the only hose you then need to check visually is the red hose from turbo to charge pipe no need to block off tip or n75 etc,,
    sounds like your issue is less of a boost leak issue, check codes no point guessing the problem but sounds like either a maf or coolant temp sensor issue if your loosing boost though it wont be the maf, if your over boosting and then going limp mode then could be split vacum line from n75 to wastgate, could be a number of things really get it on vag.com
    Last edited: Sep 8, 2009
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  16. Speedy Steve
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    Speedy Steve Active Member

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    [Sep 8, 2009]
    That was how i checked just my intercoolers and charge pipe's not the hole system. The only reason i blocked the pipes is i didnt want to preasurize the cam cover.
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  17. s3_kev
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    s3_kev Stage2'd!!!!!!

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    [Sep 9, 2009]
    you would'nt be putting anymore pressure through then you would under full boost anyway the only place the pressure you put in will go is where it does when under boost when driveing thats why its the best way to test the system as then your checking every thing on the boost circuit with out missing anything
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  18. Speedy Steve
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    Speedy Steve Active Member

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    [Sep 9, 2009]
    Yeah but i cranked the preasure up to 45psi to test it and didnt want to risk it. but from now on i know what your saying!
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  19. s3_kev
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    s3_kev Stage2'd!!!!!!

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    [Sep 9, 2009]
    45psi thats nothing i acidently got it wroung when doing mine and used the complete pressure the air compressor could produce which is regulated to 100psi, scared the poo out of me thought i was going to be wearing half my engine :keule:
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