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Boost Leak Question 2007 2.0 TFSI

Discussion in 'A3/S3/Sportback (8P Chassis)' started by Ian_UK1, Jun 17, 2013.

  1. Ian_UK1
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    Ian_UK1 New Member

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    [Jun 17, 2013]
    Hi everyone. This is my first post on the forum after about 12 months of lurking and learning!

    I'm hoping someone can help me track-down a boost leak on my 2007 2.0 TFSI.

    The car is completely standard apart from a Bluefin re-map and had been running perfectly Ok until recently, when the performance dropped away together with a marked increase in fuel consumption. The performance loss was accompanied by a faint hissing as the boost builds and a loss of torque between around 2400rpm (where the boost used to peak) and 3000 rpm. Strangely, as the rpms rise through 3000rpm, the hissing disappears and the car's performance is close to what it was before the problem appeared.

    My first thought was 'Diverter Valve' so on the ramps and under the car. Under tray off and .... there's the problem! Leaky joint on the boost pipe immediately before the intercooler (the oily mess around the joint was a bit of a giveaway). Remove pipe, clean everything fastidiously (strangely there was no oil inside the pipes, despite there being oil round the joint where the seal had gone). Fit new seals, test drive - no difference!

    Back under the car, remove diverter valve. Old diaphragm type - rev G. Fully expected the diaphragm to be split, but - like new. Clean, refit, test drive - well you can guess the outcome!

    As a precaution, I've replaced the rest of the black seals on the boost pipes with the new green ones. The jubilee clips (where fitted) are nice and tight and we know the diverter valve is good as new. But I still have a car with a boost leak because I can hear it and the performance is down accordingly.

    Unfortunately, I don't currently have a VCDS (or whatever VAGCOM is called these days) but my generic EOBD test software is showing no recorded faults - helpful these computers!

    If anyone can tell me where else I should be looking for a boost leak with the odd symptoms described above, I'd be grateful a million times over. I think I've exhausted the usual suspects and I'm not sure where to look next.

    Thanks for reading and thanks in advance if you can help me along.

    Ian
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  3. MrLapou
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    MrLapou Well-Known Member

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    [Jun 17, 2013]
    Try checking the front and rear PCV hoses.
    Could be something is popping open above a certain boost pressure.
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  4. Ian_UK1
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    Ian_UK1 New Member

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    [Jun 18, 2013]
    Thanks for the reply - I'll check these over. So far, I've only tried the 'oil-cap test' - there's a tiny bit of vacuum when removing the cap and the idle becomes lumpy once the cap's off - just as it's supposed to be.

    Do you know if there's a more reliable test to check if the PCV is working correctly? Or if it's possible for the PCV to be working correctly under vacuum, but to have failed under boost conditions?

    Sorry for so many questions - just one more, honestly! Can the evap valve cause boost loss in the way I'm experiencing?

    Thanks again in advance for any thoughts.

    Ian
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  5. OVRA3
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    OVRA3 Well-Known Member

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    [Jun 18, 2013]
    I had some oil spray on my engine and that's how I knew the pcv was on its way out. I would suggest if you have the old style pcv to change it anyway they are cheap and it will go eventually so you may as well tick that off your list as well. The other option is for 20 quid or there abouts to get a smoke test done and that will pin point any boost leaks.
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  6. Ian_UK1
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    Ian_UK1 New Member

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    [Jun 25, 2013]
    Thanks for the reply. I've now had the car smoke tested at Awesome GTi and they couldn't find anything. They removed/tested the PCV and it was apparently working correctly, same with the diverter valve. The smoke test showed no leaks whatsoever.

    But.... the problem still remains. Just because Awesome couldn't find it doesn't mean it isn't still there! The problem now goes something like this:

    If you use full throttle from 1500rpm, there's an audible hiss from the driver's footwell area starting at 2000 rpm as the boost builds, and the previous shove in the back where the car should hit max boost (2400rpm or so) is missing. If I keep my foot in, by 3000 rpm, the hiss stops and the car seems to perform normally. This suggests that the 'leak' is only happening above a certain pressure, but I've now no idea what could consistently and repeatably be holding 80% of the boost pressure, but leaking when the pressure rises above a certain level.

    If anyone's got any more ideas, I'd be so grateful to hear them as I've no idea where to go with this next.
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  7. Aidy06
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    Aidy06 Member VCDS Map User

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    [Jun 25, 2013]
    Have you tried removing the remap and seeing if the problem remains? This sounds very much like the problem I've been experiencing and I've just recently had Bluefin fitted, I've just ordered a new DV to fit this weekend when I'm home. I see you're in Manchester, I'm in Bolton. Maybe we could meet up over the weekend if I'm home and compare?
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  8. OVRA3
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    OVRA3 Well-Known Member

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    [Jun 25, 2013]
    Mine makes the same hiss and is running fine it's induction noise.. I would be inclined to go with Aidy and say its possibly the remap?

    I know a few have had problems with the generic maps on bluefin worth taking it off trouble with bluefin is there is no logging done so its hard to pin point issues.. Next step would be to get awesome to log it and maybe get it on the rolling road get an idea of what power it's running
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  9. Aidy06
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    Aidy06 Member VCDS Map User

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    [Jun 25, 2013]
    I think it has something to do with the Bluefin, my induction noise has been a lot louder since I put the remap on. I'm going to take it off this weekend hopefully and see how it runs then, cars going to an Indy tomorrow for a diagnostic test. See what's what
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  10. Ian_UK1
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    Ian_UK1 New Member

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    [Jun 25, 2013]
    Thanks once again for the replies.

    Aidy - great idea to get together and compare notes / cars / ideas - maybe we'll work out what the problem could be? It mightn't be next weekend, but I can probably do so the week after.

    OVR70N - I take your point about induction noise. If memory serves me correctly though, the car didn't sound like this when the Bluefin was first installed and the car's performance, when the hiss is present, is certainly far worse that it used to be. In performance terms, it's gone from 'quick little car' to 'yeah, whatever'!

    Drives you :banghead:
    #9
  11. OVRA3
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    OVRA3 Well-Known Member

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    [Jun 25, 2013]
    Really frustrating mate feeling your pain... When you can't find the problem it's annoying.. All I can say is mine makes a big hiss from say 2500 rpm and I had it on the rolling road and it made 260bhp.. But it does sound like you have a problem as mine is quick.. Best suggestion is go out with the indie and run some boost logs on vag com requested vs actual and that will give you an idea what's happening. I have a feeling it doesn't like the map for whatever reason. I had a hesitation issue and misfire which was annoying turned out to be plugs and a coil pack.
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  12. Aidy06
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    Aidy06 Member VCDS Map User

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    [Jun 25, 2013]
    Bluefin removed and problem gone away
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  13. OVRA3
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    OVRA3 Well-Known Member

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    [Jun 26, 2013]
    Get your money back on the bluefin and go custom :p
    #12
  14. Aidy06
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    Aidy06 Member VCDS Map User

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    [Jun 26, 2013]
    Wish I did go with Unicorn now, oh well you live and learn. I've had my Bluefin about a month now so can't return it, I'm in discussions with Superchips via email and they are looking into it
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  15. Ian_UK1
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    Ian_UK1 New Member

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    [Jun 26, 2013]
    Removed the Bluefin too - loads less hiss and the expected, substantial drop in performance.

    Then... for a bit of fun, I reinstalled it.

    What happened definitely wasn't expected - all the performance the car had when the Bluefin was first installed is back. There's still a loud hiss between 2000 and 300rpm, but now it sounds a lot less like a leak and a lot more like a small turbo working hard.

    The issue seems now like it might have been more to do with adaptation values than a continuing leak, given that installing the Bluefin resets everything to base mapping. I'm wondering if the one leak I did find - the seal on the pre-intercooler boost pipe - had caused the ECU to store some odd values? I had a not-dissimilar issue with a Bosch ECU a few years ago on a 996 Carrera - the ECU had pulled a load of timing (due to a lambda sensor fault in that instance) and didn't automatically put the timing back after the fault was rectified. Only a full reset worked the magic.

    Then again, it could be an issue with the Bluefin map, but it seems to behave very well for the most part, so I think it unlikely.

    Will report back if there's any further updates on this one.

    Thanks again to everyone for the replies and assistance.

    Ian
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  16. OVRA3
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    OVRA3 Well-Known Member

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    [Jun 26, 2013]
    Great news whooooosssssshhhhh
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  17. Aidy06
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    Aidy06 Member VCDS Map User

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    [Jun 29, 2013]
    Glad you got it sorted and are happy with it now mate, I too am really pleased with the outcome of my problems. Had my DV replaced today, the old one was absolutely ruined. It was ripped to shreds, it'd obviously been like that for a long time. New DV in and car felt so much better when I first drove it, put Bluefin back on and wow it's awesome. Car feels so good to drive, can't believe how much of a difference it has made
    #16

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