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Knocking noise on startup, before the engine turns on

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by gifuboiler, Mar 20, 2018.

  1. gifuboiler

    gifuboiler Junior Member

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    I had this weird knocking noise on startup this morning, and it happened during that time period after you turn the ignition on and before the internal combustion engine kicks on.

    Any idea what it could have been? Thanks!
     
    #1 gifuboiler, Mar 20, 2018
  2. tankyuong

    tankyuong Senior Member

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    you got oil buildup in your throttlebody.get an oil catch can
     
    #2 tankyuong, Mar 20, 2018
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  3. gifuboiler

    gifuboiler Junior Member

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    I'm failing to see how that could cause noise before the engine even tries to turn over? Can you please explain?
     
    #3 gifuboiler, Mar 20, 2018
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  4. Mendel Leisk

    Mendel Leisk Senior Member

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    I was thinking along same lines as @tankyuong , but ok, this is in the few seconds before the engine starts? There's the brake pressurizing sound. Maybe something messed up with that??
     
    #4 Mendel Leisk, Mar 20, 2018
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  5. bisco

    bisco cookie crumbler

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    agreed, not sure what would cause that. i don't recall anyone else ever bringing it up. how many seconds after you pressed the start button?

    how many miles on her?
     
    #5 bisco, Mar 20, 2018
  6. gifuboiler

    gifuboiler Junior Member

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    Yes, the knocking occurred in the few seconds between pushing the start button and the turning of the engine.

    2015, 47k miles. It occurred throughout the entire duration of the pre ignition right after pushing the start button.

    I remember reading about the knocking noise, and I initially thought that's what it was, but then I realized it couldn't have been, because the engine hadn't turned over yet.

    I used the search function and I couldn't find anything similar happening.
     
    #6 gifuboiler, Mar 20, 2018
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  7. Mendel Leisk

    Mendel Leisk Senior Member

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    Maybe you can wangle a video with the sound? I'd be hard-pressed to figure out how to do that myself, but I'm not the sharpest knife in the tech block. :oops:
     
    #7 Mendel Leisk, Mar 20, 2018
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  8. Dxta

    Dxta Senior Member

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    Can you just do a few seconds of video? That would help all of us here.
     
    #8 Dxta, Mar 20, 2018
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  9. bisco

    bisco cookie crumbler

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    did th brake accumulator make the typical sound when you opened the drivers door? maybe mendel is onto something.
    a few things are happening when you fire it up, pumps and such, so it's hard to diagnose over the internet.
    it may be helpful to have your phone recording at each start up, hoping to catch it if it happens again.
     
    #9 bisco, Mar 20, 2018
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  10. jzchen

    jzchen Newbie!

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    There is a knocking, almost like a pinball bouncing around in a pinball machine, that occurs once in a while. Happens on our v, and on my wife's '17 Alfa Romeo Giulia. Can almost feel it knocking under foot of driver footwell. When I heard the same thing in the Giulia, I knew it had to be normal, because that car just has 2000 miles on it now and was fairly new when it happened....
     
    #10 jzchen, Mar 22, 2018
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