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Now I'm Concerned: ICE Knocking on Medium Load

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by a priori, Sep 3, 2009.

  1. a priori

    a priori Canonus Curiosus

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    OK. My brand-new 2010 Prius V has been hit. Three times in three months. These weren't fun events, but so far I've survived and my car has been repaired. (Well, not quite true, as I'm still waiting to take it in since the latest hit this past Friday.)

    Now I am wondering whether I may have additional "issues."

    Just this evening I started to hear what sounds to me like a knocking sounds coming from the ICE. I've determined that the sound comes only when the ICE is running, and only when the ICE is on a medium load. By this I meant the ICE does clearly is the source of the sound, but also that the sound doesn't show when the ICE is at full acceleration.

    By using the HSI, it appears the "knocking" sound starts ONLY when the indicator shows power output to be one quarter of the way from the center line of the the HSI to the three quarter point in the "power" area -- all to the right of the center point of that meter.

    In other words, the sound isn't obvious during low-load ICE use. Also, at high acceleration (at the upper end of the "Eco" operating area and beyond), there is no sound.

    Can anyone think of what may be causing this?
     
    #1 a priori, Sep 3, 2009
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  2. bokone

    bokone Junior Member

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    Just for a quick test, run a new tankful with higher octane to rule out bad gas. Also depending on the severity of the accidents, maybe a broken engine mount?? Good luck.
     
    #2 bokone, Sep 3, 2009
  3. a64pilot

    a64pilot Active Member

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    On other cars, I would tell you the knock sensor was almost certainly unplugged during one of your your repairs . I can only assume this may be the case here as well. Engines will exhibit pre-ignition on just exactly the operating conditions you describe, High manifold pressures and low RPM. I assume when in the middle of the engine portion of the HSI the engine is operating most efficiently, Otto cycle engines operate efficiently at high manifold pressures and lower RPM, I assume Atkinson cycle is the same? Highest efficiency is obtained by riding the edge of pre-ignition by advancing the timing until pre-ignition occurs, "listening" for it by a sensor and retarding the timing until it just goes away. Not all engines are knock sensor equipped, I ASSUME the Prius is, but don't know.
    Or you could have a mechanical problem as already noted.

    On edit, Pre-ignition is what most people call "valve rattle" Is this what your describing?
     
    #3 a64pilot, Sep 3, 2009
  4. a64pilot

    a64pilot Active Member

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    Actually I believe I got it wrong, I believe detonation occurs from excessive spark lead and not pre-ignition, so just substitute detonation for pre-ignition, sorry
     
    #4 a64pilot, Sep 3, 2009
  5. a priori

    a priori Canonus Curiosus

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    Whew! Problem solved!!!

    It really did sound like the lifters, but I wondered why it would be pronounced only in the mid-range area of engine load.

    Here's what happened: The post that holds up the hood had fallen out of the clip that is supposed to hold it in place. Apparently, I had not pushed it all the way in (or someone else who was in there more recently is guilty of the same thing). For some reason, the thing made a noise only during a certain engine vibration.

    I am SOOOOO relieved!!

    Thanks to all who were trying to think of an explanation.
     
    #5 a priori, Sep 3, 2009
  6. yardman 49

    yardman 49 Active Member

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    That's great news, AP. I'm happy to hear that it was something simple!
     
    #6 yardman 49, Sep 3, 2009
  7. a64pilot

    a64pilot Active Member

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    The best fixes are the easiest ones. They stay fixed. Glad it wasn't detonation
     
    #7 a64pilot, Sep 3, 2009
  8. a priori

    a priori Canonus Curiosus

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    Thanks, folks! I feel like such an idiot to raise an alarm only to find out it was really nothing big.

    Still, I'd rather be the idiot than the guy with a real problem.

    Come to think of it, nothing has really changed, except that I don't have the problem with my Prius . . .:cool:
     
    #8 a priori, Sep 3, 2009
  9. qbee42

    qbee42 My other car is a boat

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    Resonance.

    Tom
     
    #9 qbee42, Sep 3, 2009
  10. a priori

    a priori Canonus Curiosus

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    Your answer strikes the right chord for me!
     
    #10 a priori, Sep 3, 2009
  11. jburns

    jburns Senior Senior Member

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    Just be glad you are not choice number three. An idiot with a real problem. :eek:
     
    #11 jburns, Sep 3, 2009
  12. a priori

    a priori Canonus Curiosus

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    You are making quite an assumption, here, that I am not that person.:D
     
    #12 a priori, Sep 4, 2009
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