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  1. #1
    Active Member Two Rings
    Join Date
    Mar 05 2018
    AZ Member #
    415013
    Location
    Czech Republic

    Problem after rebuild S4 B6. Cats?

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    Hi, Im new here but I've been looking for an answer for some time now and found nothing. I had my S4 engine rebuild due to excessive oil consumption (1l every 600km) and for a lack of power.
    So new rings were put in, heads were machined, faulty cam adjuster solenoid replaced, new lambda sensors, spark plugs, whole fuel system checked(new filter, everything else was good), coolant sensor replaced, cam position sensor replaced, new clutch and flywheel and the whole electric harness was checked, all four knock sensors were put in from different car, intake flap was fixed. Timing was done by previous owner and just checked.

    Things that were checked - injectors, different intake, different coils, fuel pump, ECU.

    But still the car is lacking power and drive properly only when using light throttle. More then quater the car starts to hesitate.
    If i keep the car under 2000RPM and use light throttle then everything is fine and the car pulls good. Using more throttle trows these codes:
    And the car seams to pull better when cold.

    16716 - Knock Sensor 2(G66) - Signal too low
    P0332 - 002 - Lower limit Exceeded

    17731 - Knock Sensor 4(G199) - Signal too small
    P1323 - 002 - Lower limit Exceeded

    So my mechanic thinks that the cat is probalbly clogged due to the oil consumption and these codes are thrown becouse the exhaust gases are not escaping properly. Can it be the case? I will appreciate any help.

    Btw. the car was burning oil when i bought it and I drove it approximately for 2500km before rebuild.
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  2. #2
    Established Member Two Rings
    Join Date
    May 01 2017
    AZ Member #
    398738
    Location
    Lincoln DE

    All that and didnt upgrade the top and lower left guide to metal ones.
    2008 DTM RS4

    Instagram--@tjbradney

  3. #3
    Active Member Two Rings
    Join Date
    Mar 05 2018
    AZ Member #
    415013
    Location
    Czech Republic

    I thought that the new ones are already upgraded. And honestly I dont even know if I could get one in Czech Republic.

    Hope these ones will last for some time.

    Oh and I forgot. New MAF was also tried. Almost no improvement.

    Could the cats cause these problems?

  4. #4
    Senior Member Three Rings roboto_1337's Avatar
    Join Date
    Jul 05 2016
    AZ Member #
    375740
    My Garage
    2006 S4 6MT
    Location
    Ontario, Canada

    It seems weird that a clogged cat would cause a band knock sensor IMO. Maybe purchase new knock sensors and replace them... also I'm only familiar with the two knock sensors that are under the IM. Where are the other 2 that you're talking about?

    Another thing you could do is throw some test pipes on and see if the knock sensor problem goes away.
    Piggy Pipes, Milltek non-res cat-back exhaust, JHM 93 Tune, JHM Short Throw Shifter, Updated RS4 upper and lower timing guides, Brembo 18Z w/RS4 SS lines, Hotchkiss RS4 Front Anti-sway bars, BC racing BR coilovers, EB-Works adjustable rear end links, 034 Motorsports spherical end links. 034 Motorsport Engine mounts, 034 Motorsports Silicon MAF hose, Hartmann 19" RS4 Reps +5mm 42DD front +10mm ECS rear.

  5. #5
    Active Member Two Rings
    Join Date
    Mar 05 2018
    AZ Member #
    415013
    Location
    Czech Republic

    You're right. There are only two. I was not there during the rebuild so I may have misunderstood what he was saynig.

    I could try to replace them. I will need new IM gasket right? And the torque of the sensors is 20Nm if I remember correctly?

  6. #6
    Senior Member Three Rings roboto_1337's Avatar
    Join Date
    Jul 05 2016
    AZ Member #
    375740
    My Garage
    2006 S4 6MT
    Location
    Ontario, Canada

    Quote Originally Posted by Padouch View Post
    You're right. There are only two. I was not there during the rebuild so I may have misunderstood what he was saynig.

    I could try to replace them. I will need new IM gasket right? And the torque of the sensors is 20Nm if I remember correctly?
    I would buy a new IM gasket, just to avoid potential for leaks. I can't remember the torque spec on the knock sensors.
    Piggy Pipes, Milltek non-res cat-back exhaust, JHM 93 Tune, JHM Short Throw Shifter, Updated RS4 upper and lower timing guides, Brembo 18Z w/RS4 SS lines, Hotchkiss RS4 Front Anti-sway bars, BC racing BR coilovers, EB-Works adjustable rear end links, 034 Motorsports spherical end links. 034 Motorsport Engine mounts, 034 Motorsports Silicon MAF hose, Hartmann 19" RS4 Reps +5mm 42DD front +10mm ECS rear.

  7. #7
    Established Member Two Rings Dinohodzic10's Avatar
    Join Date
    Dec 27 2016
    AZ Member #
    389200
    Location
    Baltimore,Maryland

    Had the same issue on my S4, unclogged the cat and now it runs perfect, before it had no power and would flash the cel


    Sent from my iPhone using Audizine

  8. #8
    Active Member Two Rings
    Join Date
    Mar 05 2018
    AZ Member #
    415013
    Location
    Czech Republic

    And did you have the knock sensors codes too?

    Spoke to my mechanic and he said that the same codes were there. So I'm not sure if the sensors are the problem. Wiring is ok.

    How hard is to take off the downpipes?

  9. #9
    Established Member Two Rings Mike50design's Avatar
    Join Date
    Feb 17 2017
    AZ Member #
    393471
    Location
    Mission/BC/Canada

    Quote Originally Posted by Padouch View Post
    And did you have the knock sensors codes too?

    Spoke to my mechanic and he said that the same codes were there. So I'm not sure if the sensors are the problem. Wiring is ok.

    How hard is to take off the downpipes?
    You'll need about 60-80cm worth of extensions and knuckles, but it's not the end of the world to do. Just be patient.
    2007 Audi S4 (DTM)

  10. #10
    Veteran Member Three Rings
    Join Date
    Feb 18 2014
    AZ Member #
    146977
    Location
    Arizona

    have him double check the wiring right at the end where it plugs in to the harness, on the front of the intake manifold. It's very common for the harness wires to become damaged at that spot where they enter the plug housing, they get frayed and eventually break. when they are frayed badly so only a couple strands of wire are still connected, there will be a lot more resistance which causes the low signal code. I'm betting that's your issue

  11. #11
    Senior Member Three Rings Fourpoint282's Avatar
    Join Date
    Oct 11 2015
    AZ Member #
    361428
    Location
    Atlanta, Georgia

    Iíve dot 2 stock DPs sitting in my garage if you just want to replace that piece...about 85k on the DPs. Iíll Sellíem cheap as they are taking up space...just putting that option out there


    Sent from my iPhone using Audizine

  12. #12
    Senior Member Four Rings Terry.Reese's Avatar
    Join Date
    Oct 05 2015
    AZ Member #
    359932
    My Garage
    2005 Audi Allroad 2.7 Biturbo V6
    Location
    Billings, MT

    Quote Originally Posted by Fourpoint282 View Post
    Iíve dot 2 stock DPs sitting in my garage if you just want to replace that piece...about 85k on the DPs. Iíll Sellíem cheap as they are taking up space...just putting that option out there


    Sent from my iPhone using Audizine
    He is in Czech republic if I understand correctly.
    Clarice

    JHM intake spacers, DIY intake flapper mod, ported TB, heat wrap IM, 034 motor mounts, 15mm wheel spacers, ZimbuCAI, ZimbuTune, A8 D2 exhaust manifolds.

  13. #13
    Active Member Two Rings
    Join Date
    Mar 05 2018
    AZ Member #
    415013
    Location
    Czech Republic

    Thanks for the advice and offer, but yes I'm in Czech republic. But the mechanic have some used cars, just don't have the time to install them. And I don't have the any space to work on my car for a few days. Just my driveway.

    The wiring to the sensors is fine so I guess I'll just have to wait until he has time or find someone else.



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