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MAF's and Boost Leaks --> Info please.

Discussion in 'A3/S3 Forum (8L Chassis)' started by [Dave B], Dec 23, 2010.

  1. [Dave B]
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    [Dave B] Daddy

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    [Dec 23, 2010]
    Hi All,

    I'm having boost related issues and need some info from you helpful lot. The symptoms are very little boost accompanied by an ECL which when scanned reveals this code:

    17535 - Fuel Trim: Bank 1 (Mult): System too Rich P1127 - 35-10 - - - Intermittent

    Following some googling I believe this could either be a boost leak or a dodgy MAF. I've already changed the DV for an OEM replacement so I'm ruling that out. So, my questions are:

    1. Does anyone have any diagrams of the boost pipe setup on a BAM S3 and does anybody know of common failure pipes/joins to check first? I've only scanned the pipes when changing the DV and haven't noticed anything.

    2. Has anyone successfully cleaned their MAF and if so what cleaner did you use? I've read mixed reports on the net.

    3. What's the going rate for an OEM MAF these days?

    4. What are peoples suggested next steps? I'm considering trying to run the car with the MAF unplugged to see if there's any difference toegther with checking all the pipes that could be subject to boost leaks (hence question 1 above).

    Help appreciated.

    Cheers,
    Dave.
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  3. Nilz
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    Nilz Defo worth the wait :)

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    [Dec 23, 2010]
    Firstly, try running the car with the MAF disconnected, that will put the traction control light on, but thats normal and have a good run, if its no different, then that rules the MAF out, in that case move onto piping.

    The piping, will most likely be the ones near the inlet manifold that are on their way out, also on the end of the rocker cover, there is an E shaped pipe, that can have a split in the inside of it, which is not visible until you stretch it.

    The issue I had with mine the the fuel pressure regulator pipe, so might be worth checking that too....

    As for cleaning the MAF, its not really recommended, its better to just replace it mate, think they do an exchange scheme at most places, but im not sure on costs soz.

    If you want a diagram of the pipe setup, have a look on VagCat boards (Powered by Invision Power Board)

    Hope that helps mate...let us know how you get on.
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  4. [Dave B]
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    [Dec 23, 2010]
    Thanks for the info nilz, I'll try it with the MAF unplugged tomorrow and report back.

    I've followed the Vagcat link but can't se much, I take it I need to be registered?
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  5. finesse
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    finesse Active Member VCDS Map User

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    [Dec 23, 2010]
    sounds like an issue I had relating to a dying MAF. no boost till about 5k rpm and very sluggish

    I cleaned my maf and it worked, but it eventually failed after a few thousand miles. You can get a new from eurocar parts or gsf on exchange for about 65quid

    Improved BUT sarcastic MAF clean how-to - uk-mkivs

    I had this error, running rich, turned out to be a perished hose around the evap cannister
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  6. [Dave B]
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    [Dave B] Daddy

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    [Dec 23, 2010]
    Thanks finesse, you don't by any chance know the OE part number for the MAF do you?

    And thanks for the link to the comedy MAF cleaning guide LOL..
    #5
  7. finesse
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    finesse Active Member VCDS Map User

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    [Dec 23, 2010]
    MAF - 06A 906 461 M(X)
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  8. Nilz
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    Nilz Defo worth the wait :)

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    [Dec 24, 2010]
    You do need to register on the site mate, once you are on there, you will get the view that they have in the dealers of all parts and prices too.
    #7
  9. murran
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    murran Active Member

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    [Dec 24, 2010]
    always replace the maf first with this fault code before even bothering with checking anything else.
    if it comes back (rare it does tbh).
    any sort of split hose will cause a lean mixture, unless its a purly "boosting" issue where theres an air leak under boost conditions only where the maf is reading too much air cause its leaking out between the maf and the engine..... where the muliti too rich fault code would come in..... but then you would have the accompaying "air mass to throttle valve pressure drop" fault which you apparently dont have?

    change the maf..... test and report back......
    Last edited: Dec 24, 2010
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  10. [Dave B]
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    [Dave B] Daddy

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    [Dec 24, 2010]
    I'm about to go and start some investigations but first, what behaviour should it exhibit if the MAF is unplugged and it is or isn't at fault? i.e. if it is faulty then should the car run worse or the same with it unplugged?
    Last edited: Dec 24, 2010
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  11. [Dave B]
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    [Dec 24, 2010]
    Well i've run the car with the MAF disconnected and it is exactly the same as it is with it connected. Does that mean that the maf is fine and I should continue the boost leak search?
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  12. finesse
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    finesse Active Member VCDS Map User

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    [Dec 24, 2010]
    hmmm hard to say, I'd go to halfords and get cleaner, just to totally rule out the maf

    is your car mapped ?
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  13. [Dave B]
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    [Dave B] Daddy

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    [Dec 24, 2010]
    It certainly is, everything else is standard though.
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  14. [Dave B]
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    [Dec 24, 2010]
    One other thing, if I clear the fault code via vagcom and then run the car it runs great for the first 20 odd miles then stops boosting again. From reading it seems this is down to the car recording poor running values from the sensors? Does this help shed any light?
    #13
  15. murran
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    murran Active Member

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    [Dec 24, 2010]
    with the maf unplugged the ecu can see its open circuit and will be running the engine in a safe mode.
    like wise when you delete the fault/reset the mixture adaptions, it takes time being driven for the ecu to work out theres a fault with the fueling/air. but when its recognised the fault.... once again it'll run in a limp/safe mode.
    only if the maf is really knackard will the car perform better with it unplugged. plus it also depends if the air mass is under reading (making the mixture seem lean to the ecu) the air or over reading it making the mixture seem rich).... it can go faulty either way.
    the ecu works out what the mixture should be from reading the lambda sensors.
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  16. [Dave B]
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    [Dec 24, 2010]
    Well looking at the fault it seems to be running rich so it still must be either a boost leak or a faulty MAF. I think the next steps are to keep searching for a leak and try and get hold of a security torx drive bit so I can get the MAF out if needs be. Anyone know what size the torx bit needs to be? Trust it to be a drive bit that I don't already have.........
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  17. [Dave B]
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    [Jan 21, 2011]
    Update - I've not been using the car much recently due to this on-going issue but when I have done the issue has been totally random, some times the car is fine and others it seems to not be boosting. I've constructed a pressure tester of sorts which i'm planning to try tomorrow/sunday but in the mean time i've done some logging of requested v.s actual boost:

    [​IMG]

    Any thoughts on the above?

    Also, could a broken dipstick tube cause any vac/boost problems? I know it'a a long shot but whilst hunting for boost leaks I found that the guide funnel for the dipstick was snapped, probably caused by the sh1tty garage that did the stat earlier this year!
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  18. murran
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    murran Active Member

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    [Jan 21, 2011]
    dip stick tube wants changing really, but more for oily smells than anything else. pretty easy to change anyway. have you fitted a new airmass yet? if you ha a boost leak youd have the "charger to throttle pressure drop" fault code aswell as the one you have.
    #17
  19. s3dave
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    s3dave TFSI Hybrid Supporter

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    [Jan 21, 2011]
    It looks ok to me....
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  20. [Dave B]
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    [Jan 21, 2011]
    I've not changed the MAF as I think it's ok, i'm gonna log g/s tomorrow to confirm though. I don't have any other fault codes than the one mentioned at the top of this thread...

    That's what I thought. What could cause intermitent loss of boost? Is it possible for N75's to stick/cause intermittent issues?
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  21. [Dave B]
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    [Dave B] Daddy

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    [Jan 22, 2011]
    Well after last nights logs not highlighting any issues I took the car out for a drive today waiting for it to throw a wobbler again, and bang on cue it's at it again. After about 40 miles of driving I was rounding a left hander in 4th at part throttle when the ESP light lit up on the dash (even though there was no loss of traction). After this the car pretty much ceased to boost and seemed to be running in limp mode again. As soon as I got in I did some logging of bolcks 003 and 115 and they look quite different to last nights:

    [​IMG]

    The cars also thrown up the original fault code again but this time it also threw up a MAF related fault code, the same one it threw up when I ran the car with the MAF disconnected. These faults seem to be pointing to the MAF but I can't understand how it can be fine one day and then fecked the next???
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  22. [Dave B]
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    [Dave B] Daddy

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    [Jan 23, 2011]
    Anyone? :(
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  23. s3dave
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    s3dave TFSI Hybrid Supporter

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    [Jan 23, 2011]
    Well thats why its going into limp, to much deviation from requested, maybe look at the wiring on the n75, or could be dodgy maff, maybe try cleaning it and also the throttle body , reset the adaptions and try again...
    #22
  24. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Jan 23, 2011]
    what maps on there? Celtic tuning?
    very high command request boost pressure
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  25. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Jan 23, 2011]

    dodgy connection....?
    #24
  26. [Dave B]
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    [Dave B] Daddy

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    [Jan 23, 2011]
    It's a Jabba custom map with no other mods.
    I have checked that the MAF is securely fitted and it looked fine. I'll check the connections tomorrow to see if there's any corrosion etc.

    Thanks for looking :)
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  27. badger5
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    [Jan 24, 2011]
    unless the limits have been moved, the ecu will drop into limp mode when +/- 250mb from requested boost deviates..

    logging block 115 and 118 will show the duty cycle being applied to try and achive the max'd out boost request of the map.. (flat out on request across the board!)
    #26
  28. [Dave B]
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    [Jan 24, 2011]
    Could this help identify whether its a boost leak or a dodgy MAF? I'm tempted to just replace the MAF but I'd rather not just hit and hope when it comes to replacing parts.

    On inspection yesterday I did notice that the inlet manifold had some oily residue on the outside between cylinders 3 and 4, some of the pipes beneath it also had light oily residue on them. I appreciate that this could point to boost a leak in that area but the reason I was in the engine bay was to replace a snapped dipstick guide funnel. As a result I don't know if the oil is from a leak or from the guide funnel. When the engine is idling or being revved (on standstill) should it be possible to see any signs of a boost leak?
    #27
  29. Essflee
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    Essflee Well-Known Member

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    [Jan 24, 2011]
    Funky, don't know if your tried holding the Revs at 3k when stationary, I was told to do this by Mike at Jabba a few months ago, you should see aprox 10g/s with a deviation of 0.9, if there is a greater deviation than thus then apparently it's a good indication of a boost leak...

    Not sure how far you are from Jabba but when I took a trip up there they smoke tested my car for free, which did high light a boost leak in the 'E' shaped rubber on the end of the inlet manifold...
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  30. [Dave B]
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    [Dave B] Daddy

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    [Jan 24, 2011]
    Thanks for this. I'm gonna try the 3k revs thing tonight. How exactly did they smoke test it and whereabouts did the e-shaped pipe split (inside/outside of a bend)?

    I think everytime someone finds a split pipe we should take a picture of the pipe in situ and put it in a sticky, that way we could identify the common leak points. This would at least give people somehwere to start when looking? I'll certainly be posting a picture of mine if I do indeed find one!
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  31. Essflee
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    Essflee Well-Known Member

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    [Jan 24, 2011]
    I cant remember exactly what they did when they smoke tested it, i know they diconnected the tip 'airbox side' and put a bung in it i believe and then disconnected another pipe that the hook their smoke machine up to showing an obvious leak...

    Though obvious it was, without the smoke i'd never have found it myself, even when i knew what pipe it was i still couldn't see a split, it was underneath somewhere on the inside, I suppose the biggest give away would have been the oily residue that had built up opposite the rubber pipe...
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  32. [Dave B]
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    [Dave B] Daddy

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    [Jan 25, 2011]
    Ok, I've done some more logging and I'm even more confused :(

    Following the guidance in the boost leak sticky thread I checked block 032. The first reading I took was when the fault codes were present and it wouldn't bosst (logs shown above in this thread). The readings were as follows:

    Short term adaption: -0.4%
    Long term adaption: -24.2%

    I then cleared the codes and logged them whilst the car was idling. The results are below and also include the results of logging g/s at standstill but holding the revs at 3k rpm (or as close to as I could with my ham feet):

    [​IMG]

    As per the advice above I also checked the MAF. It was securely located but I removed it to check the condition of the element, it looked clean and shiny so I promptly re-inserted it, tightened it up and made sure the clip was well connected.

    Help..?
    #31
  33. g10chy
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    [Jan 25, 2011]
    To eliminate the MAF you need to log block 002 in 3rd gear from 3k to redline....I learnt this off Welly :thumbsup:

    Remapped cars should be getting about 200+ g/s and after I put my new MAF on this is what i was hitting!!

    As above...log with VCDS and post it back up.
    #32
  34. [Dave B]
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    [Jan 25, 2011]
    I've tried this (see my earlier posts) but the problem is that one day it will reach maximum boost and hit 202g/s but the next day it will flag up the 'running rich' fault and only hit ~100g/s. Surely if the Maf is knackered it shouldn't attain the 200g/s at any point? I'm still tempted to change it but at £100 for a replacement I want to be sure it is that before I invest.
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  35. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Jan 26, 2011]
    what does block 032 say for its fuel trims?
    and block 001 during driving?
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  36. [Dave B]
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    [Dave B] Daddy

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    [Jan 26, 2011]
    Info for block 032 and fuel trim info is in the last set logs above - unless i've missed something? I'll log block 001 tonight if I get chance.
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  37. [Dave B]
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    [Dave B] Daddy

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    [Jan 28, 2011]
    I've not logged block 001 yet but I have been doing some digging. Part number 058-133-753-B shown in the picture in this thread "http://www.audi-sport.net/vb/a3-s3-forum-8l-chassis/103203-hose-pipe-help-info-pics.html" looks to have a misting of oil around it (together with some on the inlet manifold above it). If this part or a surrounding pipe is split would this cause the running rich problems that I'm seeing? Research suggests it would but I'm looking to you clever people for some confirmation ;)

    Also, how difficult is it to remove the entire section show in the pic?
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  38. [Dave B]
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    [Feb 1, 2011]
    Bump!
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  39. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Feb 1, 2011]
    yes it could do it.
    not difficult, just awkward access.
    likely a split pipe in that managerie under there
    #38
  40. seany26
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    [May 13, 2013]
    Hey Dave, I've got the same problem and symptoms you had in this post a few years back and was wondering did you get to the bottom of the problem? I've exhausted everything suggested in this thread and others. Any help would be great, thanks.
    should mention I've got fmic,beachbuggys k03 hybrid turbo.
    #39
  41. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [May 13, 2013]
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