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  1. #1
    Established Member Two Rings KunzeRob's Avatar
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    Feb 28 2016
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    369503
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    Sunnyvale, CA

    Question car vibration / cylinder knocking sensor readout

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    Hi all,

    I have a question regarding VCDS cylinder knocking readout on our V8's. Engine control block 26 and 27.

    Ever since I got the car 2 years ago, I wondered about noticeable vibrations, especially during idle. From a V8 I expect it to run smoother than a typical I4.
    I recently exchanged all spark plugs (nothing really obvious on the ones I pulled) and all coil packs with new ones as I guessed that might solve the issue. Nope... Same vibration still there. Then I went into VCDS again and looked for faults (did that from day 1 after getting the car...) and nothing there. So I looked up block 26 and 27 in the engine controller, which are the knocking sensors and it seems I have higher signals on the ones to the firewall side and the worst ones are #7 and #8. To get more clarity I divided each voltage reading by 0.117, which is the increment and posted those values next to the cylinder number for transparency.
    Attached are 3 pictures: 1) idle, 2) ~1500rpm, 3) both after swapping the injectors of #5 (best) and #8 (worst).

    My question is to all S4/RS4 owners: How smooth is your engine running and if you have VCDS, what are your block values? Am I just chasing a ghost? One comment I got was maybe I have a leakage, but that would either effect an entire bank (intake manifold) or would change during the injector swap (like an injector sealing issue). I'm running out of guesses now...

    My car is otherwise running fine. No tuning and all service done in time.

    Thanks a lot,
    Robert

    new plugs&coils - idle.jpg new plugs&coils - 1560rpm.jpg swap #5 and #8 injector.jpg

  2. #2
    Established Member Two Rings KunzeRob's Avatar
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    Feb 28 2016
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    Location
    Sunnyvale, CA

    ***push***

    Can someone provide me your engine readings?

  3. #3
    Established Member Two Rings KunzeRob's Avatar
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    Feb 28 2016
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    Sunnyvale, CA

    ***push***


    Sent from my iPhone using Audizine

  4. #4
    Senior Member Three Rings Gin+'s Avatar
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    Apr 16 2015
    AZ Member #
    327575
    Location
    CNY Syracuse

    As I understand it, the ecu listens for specific frequencies in regards to knock; independent of the measured voltage. I think of it as like having a conversation in a loud club by focusing your attention on the person who you are conversing with.
    They're not scared of you. They're scared of what you represent to 'em.

  5. #5
    Established Member Two Rings KunzeRob's Avatar
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    Feb 28 2016
    AZ Member #
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    Location
    Sunnyvale, CA

    Thanks for your response Gin+!

    I know how the sensors work, but that was not my question. My intention is to receive comparison VCDS readings from fellow B7 V8 users, which will put my readings in perspective and to receive statements on how smooth their engine runs at idle. I cannot find anything similar in previous threads or other forums...



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