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Thread: Knock sensor too sensitive?

  1. #1
    Mitsu booster
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    Knock sensor too sensitive?

    I'm running an unmodified Turbonator stage IV cal in a 87 T2 LM and seems to run fine for the most part but the CEL comes on at basically anything over 10 psi. Base timing is 12 degrees, I only run 93 octane, A/F is fine, and I don't hear any audible knock. I going to data log the knock voltage tonight. Am I missing anything that could cause a false or real ignition knock?

  2. #2
    boostaholic
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    Re: Knock sensor too sensitive?

    You should also be data logging the knock voltage threshold.

  3. #3
    Mitsu booster
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    Re: Knock sensor too sensitive?

    I will do that! Added to my gauges.

  4. #4
    Garrett booster
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    Re: Knock sensor too sensitive?

    My car was same way, make a det can and tune the knock voltage table with it. Just listen for knock and tune the table for it.

  5. #5
    Hybrid booster
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    Re: Knock sensor too sensitive?

    two piece intake ?
    do you have the support bar under the neck to head if so ?

    I've read that support bar has more to do with reducing echo from the manifold re knock sensor than supporting the intake

  6. #6
    Moderator Turbo Mopar Staff Force Fed Mopar's Avatar
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    Re: Knock sensor too sensitive?

    Quote Originally Posted by Dr. Johny Dodge View Post
    two piece intake ?
    do you have the support bar under the neck to head if so ?

    I've read that support bar has more to do with reducing echo from the manifold re knock sensor than supporting the intake
    Now that is something interesting I hadn't thought of.
    Rob M.
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  7. #7
    Mitsu booster
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    Re: Knock sensor too sensitive?

    Interesting. But no, it's a one piece.

  8. #8
    Mitsu booster
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    Re: Knock sensor too sensitive?

    Here's a video of a quick pull. It wouldn't let me go over 10 psi and the cel flashed once in second gear. https://youtu.be/PULG2bBj8XA

  9. #9
    turbo addict
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    Re: Knock sensor too sensitive?

    Highest knock voltage I saw was .59V, on a 0-5V scale, it's pretty much nothing.

  10. #10
    Mitsu booster
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    Re: Knock sensor too sensitive?

    Yeah I just don't understand why the cel would come on. There are no codes stored like if something else is causing it.

    Here's a video of the cel coming on.
    https://youtu.be/KAghwTrzxj8

    And here's the log of that run.
    https://youtu.be/-lkkxC31dNQ

  11. #11
    Supporting Member II Turbo Mopar Contributor
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    Re: Knock sensor too sensitive?

    I thought I was having a similar issue. I never heard knock, the car ran awesome, made good power, A/F was good, even was running water/meth injection (which I believe kept the car together). Years later I *finally* popped the head gasket bad enough that I had a miss. Pulled the head...I suppose I *was* having knock! LOL The gasket was blown all over the place, pistons showed signs of very light pitting and the rod bearings were pretty beat.

    I know this doesn't help solve your issue, but the take-away should be you probably are having knock, just really light knock. It may be that it just needs a slightly less aggressive timing ramp.

  12. #12
    turbo addict
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    Re: Knock sensor too sensitive?

    Don't trust that CEL light, always look at the voltage.

    Here is the RPM vs knock voltage table. Anything below the blue line is considered "noise" and not knock.


  13. #13
    boostaholic
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    Re: Knock sensor too sensitive?

    You should also be logging RET to see if the ECU is actually sensing knock and pulling timing.

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