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Strange Loss of Boost?

Discussion in 'A3/S3 Forum (8L Chassis)' started by S3 Paul, Nov 30, 2009.

  1. S3 Paul
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    S3 Paul Active Member

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    Ive had this problem happen twice now and its confused me,
    It seems to happen when i have left the car for a while ( a couple of days) and then drive it steady once the car has wamed up and i go to stretch its legs a little i only get around 11psi of boost , I know this is what the waste gate is set to.
    The first time i thought maybe the N75 had come unpluged or loose so i turnedthe car off and had a poke around, When i fired it up to head home everything was fine. full boost again!
    I had a spare N75 valve at home so i tried that and things seemed ok... untill this morning, Same thing, Only 11psi until i tuned engine off and on, Then everything is fine
    Has anybody any ideas?
    I dont want to just chase the problem around the engine bay buying expensive sensors and valve if i dont even know where it is
    #1
  2. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    DIS showing the frost warning by chance? (5deg or less)

    <tuffty/>
    #2
  3. pauldazzle
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    pauldazzle Active Member

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    Sounds like your car is going to limp mode. You need to get Vagcom on it & check for fault codes.
    #3
  4. S3 Paul
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    S3 Paul Active Member

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    It wasnt realy cold this morning to be honest,
    If it was hitting limp mode would it not make a dash light come on? It has in the past. when it blew a boost hose off.
    Ive checked backdown the wires for the N75 and cant see a break or anything.:keule:
    #4
  5. NHN
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    NHN Modmetractor

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    Unless somethings sticking mate on 1st start up & then when you turn of its removing pressure & then when you start up again its released the component from the turn of & the cars boosting properly again on 2nd start, if you get me, kinda like a valve stuck say corroded/blocked water valves have been known to do this, not sure my analogy makes sense but from your experience it seems possible.
    #5
  6. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    Do you have Custom Code? I had this same prob although it did put the ESP light on the dash. I would start the car first thing in the morning and if the 'frost' indicator was on the DIS then it would work on actuator pressure only but if I turned off the ignition and restarted the car straight away it would be fine...

    Turns out its something in the Custom Code remap I had thats a fail safe on the std map. Got it coded out and all was fine again.

    <tuffty/>
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  7. 1animal1
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    1animal1 The Clar!! it mouves!!!

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    whats this Tuft? ive never noticed any difference on mine, frost indicator or not? is it a minimal diff or are we talking night and day.....
    #7
  8. s3_kev
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    s3_kev Stage2'd!!!!!!

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    are you still using the n249 valve?? only reason is that i once reomved the hose that leads off to the dv with the rest connected and my boost would only go to around this figure untill i reconected the hose, check its not split anywhere may have been just because i enduced a boost leak though and that was its peak boost it could create, so check boost and vac lines for splits etc..
    #8
  9. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    Was night and day mate, boost gauge showed 0.5bar when it happened (normally 1.1ish bar under boost) and ESP light stayed on... restarting made it go straight away... can't remember the fault code it threw but was something about a pressure differential and to check DV!!... bizarre.

    <tuffty/>
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  10. pauldazzle
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    pauldazzle Active Member

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    Some codes don't trigger the malfunction light.
    I had code 17705 (pressure drop between throttle body & turbo) on one of my remapped MK4 Golfs. It never put the malfunction light on, but car would go into limp on start up, & clear on restart.:banghead:
    Last edited: Nov 30, 2009
    #10
  11. jonny87
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    jonny87 Active Member

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    i had something similar on my s3, like you, would warm her up then go put put my boot in and mine would stick at 8-9psi, keep going steady down the road, put the boot in again and all was well boosting to 18-19psi as norm

    this happened a handful times after visiting jabbasport, vagcom was plugged in a number of times with no faults showing, was told it could be one of two things:

    incorrect actuator arm setting/actuator arm sticking

    this second one is probably not relevant to you, but seeing as mine has blown it turbo a few times i was told its possible that a crack somewhere in the exhaust port has been missed and giving a small boost leak (mine also seems to lack lowdown torque/power)

    but for the last month or so this has not occurred, i havent done anything to try and rectify the fault, it hasnt even been looked at for this reason, put it down to sticking actuator arm!

    is it possible this is the same on yours if you are leaving it standing for a few days at a time, especially with the wet and cold weather now here?
    #11
  12. 1animal1
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    1animal1 The Clar!! it mouves!!!

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    aaah, just wondered cos my ESP light has been known to appear mid drive on occasion....no power differetial though in the 18months ive had the map :salute:
    #12
  13. S3 Paul
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    S3 Paul Active Member

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    Well its driven fine home... plugged in the laptop and thats the fault code i have,

    I do have custom code phase 3 on my car, the turbo is about 6mth old ,
    It was 3.5 degree on the way home and boosted normaly.
    #13
  14. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    Yup, sounds the same as I had.... Bill asked James to code it out...

    <tuffty/>
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  15. S3 Paul
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    S3 Paul Active Member

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    I dont get the esp light on...
    could this still be the same?
    This code has apeared before to be honest but now i am running higher boost the drop to gate preasure ( and the tell tail gauge ) is sooo much more obvious.
    #15
  16. pauldazzle
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    pauldazzle Active Member

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    When I had this, it turned out to be a software glitch, but you well may have a boost leak somewhere.
    The first place I would look for a boost leak is the braided pipe on the inlet manifold & the braided pipe on the plate where the N249 & N112 are situated. Both the pipes are prone to splitting & because of the braid it's hard to see if there's a split. The big rubber pipe from the pancake pipe to the intercooler is also a weak spot.
    It's worth taking a look at this. http://uk-mkivs.net/forums/t/170257.aspx
    #16
  17. S3 Paul
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    S3 Paul Active Member

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    So if i ring jbs and ask about this what do i call it ?
    Will they know what i mean?
    Is it a system that can be turned off such as the post cat lambda?
    Is it safe to do?
    #17
  18. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    Can't remember what it is Bill said James did tbh... Pretty sure this was the fault code thrown...

    http://wiki.ross-tech.com/index.php/17705/P1297/004759

    Really weird as I would start the car first thing, put it in gear and move off and it would fault straight away, restart the car straight away and no probs... only ever did it when frost warning was on. 5.5 degrees was fine, 5 degrees and it would fault and run 0.5bar. Repeatable every time.

    Mine was a CC stage 1 at the time mind, can't comment on the stage 3 but guessing its similar code.

    I think the definition of 'safe' is more down to you not ragging the car before it warms up properly.... JBS 'should' know about it, if not then Bill should remember.

    Just tell them the symptoms... they should realise what it is from that.

    <tuffty/>
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  19. S3 Paul
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    S3 Paul Active Member

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    Well i do have another boost control valve in my tool box i might try fitting at dinner time.
    But i will ring jbs and speak to james too
    #19
  20. S3 Paul
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    S3 Paul Active Member

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    Just a little update...
    I set off for work this morning hoping it would be a cold one... by jove it was! -1.0 degree and again i had only 11psi of boost, I let her warm up fully before trying to make boost obviously, Then before i turned the car off i ran a fault code scan... same one again preasure drop between turbo and throttle valve ... i turned the car off, restarted and carried on with my drive to work, this time making a happy 23psi of boost. while letting the car cool down at work i ran the fault scan... nothing this time !
    #20
  21. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    same mate... same... speak to JBS...

    <tuffty/>
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  22. NHN
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    NHN Modmetractor

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    Throttle valve, is this the TB as such, I cant recall from my S3 tbh, all these differing names, any pic of the part?
    #22
  23. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    Pretty sure you are having the same software issue I had mate....

    <tuffty/>
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  24. S3 Paul
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    S3 Paul Active Member

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    Ive rung JBS and await the call back,
    If this is the same as what you had tuffty... i owe you more than a few beers !
    Bloody car is driving me mad.
    Its become known as the porcelean (if thats how you spell it ) car, If it is a safety thing left in because audi saw fit to use it in the first place i expect i will end up paying for it. But if its a floor in the map hopefully it willnt hurt the bank balance too much.
    #24
  25. NHN
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    NHN Modmetractor

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    Cause I'm wondering if its a sticking flap in the cold that gets jerked by the boost on/off/on to function properly, possible solder joints on the flap pcb not liking the cold, speculating but think you see my thought process, although as few have had after the same maps it would seem logical this is the problem, but always best to look at all issues, do you think the map is effecting the flap as such, if this is the throttle valve

    Then again is the boost pressure sensor before the flap or after in the intake mani etc, as before then would detect a fair bit of boost, after would detect the lower boost huh.
    #25
  26. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    All I will say is that after a code change, mine was cured... I had a CC stage 1 from Bill, all was good until it starting getting cold then I had the exact same symptoms as above.... Bill told James, James sent another map file, Bill flashed my car... fixed... simples

    <tuffty/>
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  27. NHN
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    NHN Modmetractor

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    Be interested to know what they change in the map to fix this, Tufty can you get anymore info on this please mate, curious, cause from where I'm sitting it would indicate the boost is being blocked if the error report above is correct, only thing that could do this as he hasnt got a leak is the flap surely
    #27
  28. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    Will do... I'll ask Bill next time I see him.

    <tuffty/>
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  29. badger5
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    badger5 RIP S3dave Site Sponsor

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    its code, code was changed eventually by james, and reflash made it go away
    its not a cc bug, its inherant in factory code, as well on all 210/225 motors

    the differential is much bigger hence more noticable on chipped cars
    #29
  30. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    Ahhhh, that was it :)

    <tuffty/>
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  31. pauldazzle
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    pauldazzle Active Member

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    When this was happening to me, I found that if I started the car from cold with some revs on it wouldn't throw the code. If I started & let it idle for a a few seconds it would throw the code. The guy who'd originally remapped the car went AWOL, & in desperation I had the Revo trial loaded in because I was suspicious that it was a software issue, & it didn't throw the code. When the trial ran out it was fine too. Had the car Revo'd a month or so later & never saw the code again.:yahoo:
    So my bet is that you have the same problem & getting the ECU flashed again will solve it.
    Last edited: Dec 1, 2009
    #31
  32. S3 Paul
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    S3 Paul Active Member

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    Well i spoke to Mike today at jbs and he spoke to james while i was on the fone... he said ok, bring it up, we will sort it,

    Hope it is a simple as that !
    Mind i did add that i would like the map reworking on the dyno to up things but only inside the limits of the turbo.
    We shall see, friday is the day !!
    #32
  33. S3 Paul
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    S3 Paul Active Member

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    Just wasted 4 hours of my time
    Booked in at jbs at 1pm just left with nothing done at all.
    Good work James,
    #33
  34. NHN
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    NHN Modmetractor

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    Why so mate?
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  35. S3 Paul
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    S3 Paul Active Member

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    He chose not to turn up.
    #35
  36. NHN
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    NHN Modmetractor

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    WTF u for real?
    #36
  37. S3 Paul
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    S3 Paul Active Member

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    No joke,
    I only wish i was,
    #37
  38. NHN
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    NHN Modmetractor

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    That doesnt exactly put him in good stead huh, hope he had a good reason as he could of at least called you to advise he wouldnt be in, I mean seriously thats very very rude.
    #38
  39. Dani_B19
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    Dani_B19 Audi-sports own special child.

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    Thats disgusting, thats a perfetic excuse, he should have at least contacted you, after all the time and money you've spent with them.
    #39
  40. S3 Paul
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    S3 Paul Active Member

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    Well the ecu has been reflashed with the cold weather/low boost setting issue coded out... time and a few cold mornings will show if its worked.
    Ive got to log a few things and send the files over to be sure all is well.
    #40

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