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TDi down on power

Discussion in 'A3/S3 Forum (8L Chassis)' started by anilkumar, Aug 14, 2010.

  1. anilkumar
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    anilkumar Member

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    [Aug 14, 2010]
    i just got a 1.9 tdi 130 can hear turbo spool at around 1500 rpm to 2300 rpm but the turbo whistle sems to disapear after 2500 rpm to be down on power dont get a surge of power at 2000 RPM any more like it used to since its been down on power the car dose not smoke at all


    thanks
    Last edited: Aug 14, 2010
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  3. sportstractor
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    sportstractor Chugger

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    [Aug 14, 2010]
    possible maf.

    Need to get it vagcommed.

    This forum aint to handy for diesels, might be worth posting on ukmkiv's
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  4. murran
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    murran Active Member

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    [Aug 14, 2010]
    some of us are quite good with diesels tho........

    sounds like the variable vane system on the turbo not working right.
    functional description;
    vacuum is supplyed from the brake servo pipe down a little vac pipe to an actuator valve. this actuator valve is switched in and out by the ecu on a varying duty cycle according to running conditions. to supply certain amounts of vacuum (down another little vac pipe) to the variable vane actuator on the side of the turbo.
    theres a mechnical set of vanes inside the turbo that can move to direct the exiting exhaust gas into the impeller or away from it.
    this system allows the ecu to vary the turbo speed/supplied boost to the engine. example, allowing the ecu to spool the turbo up at lower revs or drop it off at high revs low throttle......

    common faults are;
    -the turbo vanes sooting up inside the turbo and seizeing up. usually you get over boost fault codes.
    -vacuum leaks from split vac pipes rubbing on things and wearing through.
    -the actuator valve can go faulty. where the valve actuates fine but leaks vacuum back.

    from the description of your fault, id put a tenner on it being the valve. theyre mounted on the baulkhead to wards the n/s. theres two or three of them (the other valves work the egr valve and "stop" flap on the inlet manifold). you'll need to identify which one it is by following the vac pipe from the turbo acuator. the actuator valves are about £40 i think?
    Last edited: Aug 14, 2010
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  5. murran
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    murran Active Member

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  6. anilkumar
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    anilkumar Member

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    [Aug 14, 2010]
    thanks for the info if the turbo vanes were sticking would car going in to limp mode because it dosnt sound like its going in to limp mode
    looks like i will have to get it scanned this valve u mentioned is it the n75 have u got a picture of the actuator valve
    #5
  7. murran
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    murran Active Member

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    [Aug 14, 2010]
    they look like the one in the ebay link above.

    if the vanes in the turbo are seized, they seize in the boosting position. which is why you get over boost fault codes, as the ecu is trying to back the boost off using the vanes but the boost pressure sensor is seeing overboost.
    when this happens the ecu will limit the fueling so it doesnt start bending conrods. you'll feel a drop off in power, but when you turn it off and back on again this resets. it'll feel fast again, till the second or thrid time you boot it, it'll see the overboost again, and the power will drop off.

    your describing, on accelaration, an initial boost then it weeding off? the same everytime you accelarate?
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  8. anilkumar
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    anilkumar Member

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    [Aug 16, 2010]
    yea its the same every time you accelarate turbo come in at around 1500RPM and seams to disapear at around 2500 rpm car is able to 70+ on the motorway so i dont think it is overboost problems going to get it hocked up to vagcom see what happens
    #7
  9. jojo
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    jojo S3 Drift King! Staff Member Moderator

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    [Aug 16, 2010]
    You could try and drive your car with the MAF unplugged, it will be running with less power than standard, buy should still rev cleanly throughout the rev range. This will test out if the MAF is faulty.
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  10. lewis88
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    lewis88 Member

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    [Aug 16, 2010]
    this sounds like mine, although i didn't notice anything was wrong as its done it ever since i bought it. what should it hold a decent amount of boost to? mines seems a bit weak after 2.5k?? or am i just being paranoid?
    #9
  11. MURRAYS444
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    MURRAYS444 Member

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  12. anilkumar
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    anilkumar Member

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    [Aug 16, 2010]
    mines used to pull like a train and give a nice surge of power up to 3500rpm now power is **** and no turbo after 2300RPM but turbo comes in nicely at 1500 RPM-2000 rpm when i let of the throtle at around 2500rpm i get a dump valve sort of noise
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  13. murran
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    murran Active Member

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    [Aug 17, 2010]
    if you look at the actual values on the diagnostics while driving the car.... you'll see that the airmass intake figure depending on what bhp the car is will go up tp 850 to 1100 grammes of air per second on full boost. unplug the airmass and the ecu leaves it on a safe 550 grammes per second all the time. unless the airmass is totally fucked...... unplugging it is not a good test on whether its working or not!
    Last edited: Aug 17, 2010
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  14. jojo
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    jojo S3 Drift King! Staff Member Moderator

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    [Aug 17, 2010]
    If the car is struggling to go past 2.5k, then unplugging the MAF as a test to see if it effects performance won't harm the car right? I'm not saying it's a full proof way of testing it, but just a way of testing if the fault is MAF related?
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  15. anilkumar
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    anilkumar Member

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    [Aug 19, 2010]
    i have had a diagnostic check done today and it came up with a fault for the maf sensor the airmass intake figure was low also had the EGR valve checked and it was full of **** and was casueing the valve to stick so i got it cleaned i recomend that everybody should clean thier EGR valves out as it has made a difrance to the car i just need to get a new MAF sonsor
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  16. Turkster
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    Turkster Bro.Paul 2.5TDI Quattro Sport

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    [Aug 20, 2010]
    Some good info in this thread,

    My 2.5 TDI is having an small issue, from stand still if you floor it the power is just not there, she takes off at an ok speed, by the time the car has choked to the end of the gear it flys off in 2nd gear a lot better and the turbo kicks is, 3rd,4th, 5th and 6th are there ok,

    I unplugged the EGR valve and wooosh off she goes like a bomb, but pipe that goes onto the EGR valve is not blocked so its classed as leaking? when i block the pipe with a bolt the car takes off ok but not as powerfull, The EGR valve is on 2 years old as iv changed it before, the pipe that connects to the EGR valve is sucking good,

    Do you think it could be the actuator on the Turbo sticking ?
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  17. anilkumar
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    anilkumar Member

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    [Aug 20, 2010]
    the valve coulde be sticking have u had it scaned
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  18. Turkster
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    Turkster Bro.Paul 2.5TDI Quattro Sport

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    [Aug 22, 2010]
    should be done on sunday
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  19. adamss24
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    adamss24 Well-Known Member

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    [Aug 22, 2010]
    You can block the valve at the manifold side with a thin metal gasket between the matting faces. I have done-it for years or you can reduce the oppening of the EGR valve with vag-com, login code 26262 in basic setings block4. Increase the value eg: 32768 to the highest value the ECU will accept, tipically 33638 or there abouts. The valve will still work within the factory spec but will clog on a much much slower rate(Disclaimer: For Off Road Use Only !). Not every ecu will accept the 26262 login code so if the ECU drops connection with the VCDS then it wont work.
    #18
  20. anilkumar
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    anilkumar Member

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    [Aug 28, 2010]
    i have got a new MAF sensor for £80 from GFS audi wanted £159 fited to the car and it now semms to be fine also had to change fuel temp sensor and temp sensor
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  21. lewis88
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    lewis88 Member

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    [Aug 28, 2010]
    ive just heard that sort of dump valve noise on my car at 2.5k. im planning on getting the car diagnostic scanned but before that im going to clean the MAF sensor and EGR valve just incase.
    anilkumar, did your car take a while to warm up? and did it seem slightly better when it was warm? apparently eurospares or europarts do the bosche OEM MAF sensors for £36, im just sourcing the other parts now.
    #20
  22. anilkumar
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    anilkumar Member

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    [Aug 29, 2010]
    eruo carparts quoted me me £120 for a maf did two trips 2 birmingham to coventery over the last 2 days car seems to be fine sum days and then semms to have no boost above 2300k rpm at times restarting the car has no difrance no fault codes coud it be a fault with the N75 dont think it is going im to limp mode car can do 70 +
    Last edited: Aug 29, 2010
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  23. anilkumar
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    anilkumar Member

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    [Aug 30, 2010]
    it sems ti warm up ok car feels the same when its warm
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  24. ruffrida
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    ruffrida Well-Known Member

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    [Apr 26, 2012]
    This defo sounds like your vanes are stuck in the turbo, i had a really bad over boost problem with my 110 tdi - 2000 plate, i have taken my turbo to be reconditioned as the vanes where that bad it nearly seized me turbo. Hopefully be all good when i get it back tomorrow.
    Before all this i changed the N75, maf sensor, all the hoses (for nice red ones), and none of it fixed it, made it better but did not fix it.
    You could try the Mr muscle vane cleaner, go on my home page and look under threads started by me, its called how to get more bhp from your tdi ( i think), works awesome for some people, didnt work for mine as it was to far gone.
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  25. ruffrida
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    ruffrida Well-Known Member

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    [May 8, 2012]
    Be nice to know how you got on here bud, as i have replaced me maf sensor, cleaned egr, and blanked it off, all hoses replaced, new turbo and still goes into limp mode in 4th gear at about 2500revs.

    Any ideas guys??
    #24

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