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Thread: Knock Knock

  1. #1
    Join Date
    Jul 2003
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    Knock Knock

    I was reading in another thread about the unhearable knock and the knock sensors detecting said knock and the computer doing what it does in response.

    Since I theoretically can't hear the knock but the computer can, is there a tally kept by the computer for the technician to view? Is there a real time gathering device I could leave plugged into the ODBII connector that could do this?

    I don't suspect a problem but it would be interesting once a month or so to go for a "diagnostics" run and see the "knock" tally among other things.
    Dave

  2. #2
    Join Date
    Nov 2002
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    Off-Shore America
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    I have had the same question for a while now, with no positive results. Nor have I seen this 411 reported in OBDII data dumps. If and when you find a scan tool, please grab one for me?

    I slightly recall something from the Buick GN peeps, something made from Radio Shack stuff that used dash mounted LEDs to report sensor activity, but this is all I recall.

  3. #3
    Join Date
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    St. Clair Shores, MI
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    Knocking

    When the sensor detects a knock, the PCM reduces the spark advance momentarly (to clear the knock) then advances back to the advace that is considered optimum. The only systems that I'm aware of for detection and recording, are the systems used in testing.
    2004 Marauder/ 1994 Thunderbird SuperCoupe/ 1983 Mustang GT

  4. #4
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    Hmmm... pretty sure I saw SCT software logging it real-time during a dyno pull.

  5. #5
    TripleTransAm Guest
    I'll have to dig out my laptop to check my Ford version of Autotap, but I know my GTA's pre-OBDII PCM (even before they called it OBD-I !) will record knock counts. I think it's a one-byte value in my GTA (0-255, then it wraps around and continues counting). I'd be disappointed if the new / improved PCMs don't store this info.

  6. #6
    Join Date
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    Slickville, PA
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    http://www.jandssafeguard.com/

    http://www.american-pi.com/safeguard/safeguard2.html


    there are a few companies out there that make timing retards the use knock sensors.


    "The knock retard system is beautiful. It has the ability to retard ONLY the offending cylinder(s) that cause the knock. It does not retard the baseline ignition setting on all cylinders."


    always told myself I would use one if I got a blower....
    2003 300A "Morticia"
    2009 Expedition
    1996 E250

    FASTEST SPEED POST: 25WPM at 78MPH
    (can only improve with practice)

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