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Surging/bellowing???

Discussion in 'Audi S4/A4/A4 Cab (B7 Chassis)' started by Newbos, Oct 18, 2012.

  1. Newbos
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    Newbos Member

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    [Oct 18, 2012]
    Guys 2.0 TDi 140

    Not sure how to describe this, so i hope it makes sense ;)

    Ill try and describe the symptons

    while accelerating from stand still or being in a low gear the car seems to make a bellowing sound (first of all i thought this was road noise, but it does all the time unless i hardly press the throttle at all)

    When i took more notice of the sound i also noticed the car seem to surge when this was happening almost like i was getting more boost for a split second.

    I hope that makes sense. I have had the car nearly two months and it has done it from day 1, it doesnt effect my MPG i dont think, i get 650 miles to a full tank driving it normally. I have stripped the EGR and cleaned it even though it wasnt too bad and it may sound like a silly question but do these cars have a recirculation valve? could the diaphram be knackered?

    Any ideas?

    VAG COM shows no errors also.

    Thanks
    Simon
    #1
  2. Newbos
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    Newbos Member

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    [Oct 19, 2012]
    Anyone? Sorry to be impatient. :)
    #2
  3. VagPro
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    VagPro Active Member

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    [Oct 19, 2012]
    Bellowing sound? Might have more luck if you can record it....
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    ChrisShepB7 likes this.
  4. Newbos
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    Newbos Member

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    [Oct 19, 2012]
    Its a bit hard to record as it sounds like road noise, but to be honest i think its just me hearing things. I think the actual fault is the boost surges for a split second, (i suppose it feels like a blockage and for a split second it clears)
    #4
  5. sidibear
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    sidibear Looking for Zombies !! Staff Member Moderator

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    [Oct 19, 2012]
    Air leak on an inlet hose?
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  6. Newbos
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    Newbos Member

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    [Oct 19, 2012]
    it could be i suppose, but if i drive hard the car is fine. It only seems to happen when i drive normally.
    #6
  7. Newbos
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    Newbos Member

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    [Oct 21, 2012]
    Do these cars have a n75 valve? Could it be that?
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  8. Wrath
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    Wrath Well-Known Member

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    [Oct 21, 2012]
    Not a split intercooler hose?
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  9. Newbos
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    Newbos Member

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    [Jan 3, 2013]
    Hopefully maybe getting somewhere on this. The bellowing sound is down to the rear tyres having a flat spot, so they are getting changed, but the surging it seems is down to a boost solenoid. When accelerating the computer says its running 50% and then it drops to 4% and then back up to 50% so thats the surging so I'm hoping this fixes it.
    #9
  10. Newbos
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    Newbos Member

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    [Jan 10, 2013]
    I have changed the pressure converter solenoid and it has made no difference at all :( im completely at a loss now. There are no cracked pipes, no VAG COM faults and the only thing it shows is a drop of boost on the readings and then it surges up to the correct amount of boost.

    Any suggestions?

    Si
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  11. Newbos
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    Newbos Member

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  12. Newbos
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    Newbos Member

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    [Jan 10, 2013]
    Something was bothering me about my recent trip to my Audi specialist... The receipt I got shows my engine code and it states it's a BRE engine and clear as daylight it says it on the engine and it the boot. So tonight I ran a check using vag com and that says I have a blb ecu. Wrong ecu in car??? Surely not
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  13. VagPro
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    VagPro Active Member

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    [Jan 11, 2013]
    Hello newbos,

    I am not an expert on this topic but have some information which may be of use. Find links to the VW SSP's for your engine, a similar engine and Variable Turbochargers

    SSP_316 The 2.0 ltr TDI engine.zip
    SSP 209 1.9 TDI Engine with Pump-Nozzle Injection System
    190 Variable Geometry Turbocharger

    Given what you have described it appears though the ECU is telling the N75 valve to reduce the Turbo Pressure and hence the flat spot / loss of power. Maybe you could try plotting the ECU Demand Pressure vs Actual Pressure and see if there is much deviation? Maybe the turbo vanes are sticking causing an overboost and when the N75 tries to compensate the turbo vanes stick and when they do move the pressure is too low ? Is it possible to see the signal going to the N75 from the ECU ? Just an idea....

    The parameters should be found on measuring block 11 (see also link below)

    Ross-Tech: VAG-COM: TDI VAG-COM Info
    #13
  14. Newbos
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    Newbos Member

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    [Jan 11, 2013]
    Cheers for this, however this is where my knowledge stops so what you are asking is above me, but i can try and find out some more from my mate who is an audi mastertech. I have just rang my local audi dealership as well and my car does have the correct ECU in the car. To be honest it does feel like the vanes are sticking which is a worry in its own, because i dont want it to be the turbo as they cost a fortune to replace. :(
    #14
  15. VagPro
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    VagPro Active Member

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    [Jan 11, 2013]
    If you have Vagcom, looking at the actual vs demand boost is quiet simple. If it is the Turbo vanes that are sticking, the Turbo can be removed and cleaned. (or if you are feeling brave you can try the oven cleaner trick, which can be online but I do not know what the long term effects are)
    #15
  16. Newbos
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    Newbos Member

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    [Jan 22, 2013]
    Another update on this! Had it in at Audi because I was fed up of different garages scratching their head. Anyway Audi first did all the norm checks including values from n75, maf etc.. All was well. They tried updating the ecu but there isn't an update for my car. It's in again on Thursday and they are going to try another ecu from another b7 tdi with matching ser no. Part of me is hoping this will fix it, but it's nearly £800 for a new ecu :(

    I hope If anyone else has this issue they can look at this thread and feel they aren't alone as I'm going mad trying to solve this issue.

    Simon
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  17. Newbos
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    Newbos Member

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    [Mar 15, 2013]
    Right, brand new ecu in car and my fault has gone!!! My car now feels great to drive. Happy days!
    #17
  18. scotty76
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    scotty76 Well-Known Member

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    [Mar 15, 2013]
    Glad you got it sorted and thanks for posting the follow up. So many of these threads never have a resolution posted so if you find it later on Google you are left wondering what happened. :)
    #18
  19. Newbos
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    Newbos Member

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    [Mar 15, 2013]
    No problem just glad it got sorted so I can enjoy the car now and get some decent mpg.
    #19

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