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Knocking noise at startup

Discussion in 'Prius c Care, Maintenance and Troubleshooting' started by markp13, Apr 18, 2017.

  1. markp13

    markp13 Junior Member

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    2012 Prius c
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    N/A
    This post relates to a loud knocking sound that is only occasional. It most often happens when the Prius C has been shut off for some time – or when it has been shut off for a while, moved a short distance and restarted some time later. It has happened in both cold and warm conditions.

    I am posting video documentation and a brief description of my experience with the hope that other Prius C drivers with this issue will document and report it to Toyota. Currently there are no TSB's specific to this issue and I have received no fix from Toyota.

    Please note, in the 3 examples below, the volume has been increased slightly so that you can better hear the noise.



    In the video, my text says "engine knocking" but my mechanic suspects this could be cam phaser related. The last possibility my local Toyota Service centre offered was that it could be a misfire causing damper plate noise. A mechanic from the official Toyota Dealer I bought it from (I since switched to a different Service Centre!) stated that it was "missing", but their written invoice said the noise was "normal" and the result of the "engine to electric motor coupling."
     
    #1 markp13, Apr 18, 2017
  2. Samprocat

    Samprocat Active Member

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    This more related to fuel quality
    How often you feel your tank
    Do you have water in the tank
    Check your spark plugs
    Inspect egr valve
    Throttle body valve
    Look for excessive oil residue in intake manifold
    Even spark plugs bought from Toyota should be check for gap
    What one of mechanic tell you for cam phase switch noise is true
    Inspect cam phase solenoid
    This if get malfunctioning will make this sounds....metal debris and wear will lead to erratic cam phase operations


    Posted via the PriusChat mobile app.
     
    #2 Samprocat, Apr 18, 2017
  3. Samprocat

    Samprocat Active Member

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    #3 Samprocat, Apr 18, 2017
  4. Samprocat

    Samprocat Active Member

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    Before you do anything try to use 91 octane 100% fuel and aftet second tank sse if this still is issue
    Misfire is usually related to bad fuel and tune up
    Since this is happening on warm and cold
    I will suggest try better fuel

    Posted via the PriusChat mobile app.
     
    #4 Samprocat, Apr 18, 2017
  5. markp13

    markp13 Junior Member

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    N/A
    - Tank is never less than half full. 87 Octane is recommended in the manual so this should not be an issue, and if it is an issue, Toyota is being dishonest.
    - No water in tank.
    - I am not a mechanic. Toyota cleaned intake manifold and opened up engine. They say they found no problems.
    - My car only has 43,000 km on it right now and this started when it had WAY less kms. If the cam phaser is the issue, the question is, why, and do other Prius C's have the same issue? The service centre could not reproduce the issue with a computer hooked up the second time I bought it in. They say they tried every day for a week.
     
    #5 markp13, Apr 18, 2017
  6. Nathan Posell

    Nathan Posell New Member

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    #6 Nathan Posell, Jan 14, 2019
  7. Nathan Posell

    Nathan Posell New Member

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    I have this same problem and the diagnostic pulled up as a missfire. My engine light also came on after this happened. I went ahead changed the plugs and coils and is still happening. It also feels like the transmission is slipping at time when accelerating after the battery disengages. Any thoughts? Could it be the fuel injectors? Thanks
     
    #7 Nathan Posell, Jan 14, 2019
  8. DYang559

    DYang559 New Member

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    Any solution to this possible “engine” knocking?
     
    #8 DYang559, Mar 7, 2020
  9. iceman13

    iceman13 Member

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    After trying using Techron and other fuel injector/system cleaners I found out that what resolved the issue for me is using 91 octane fuel or higher. It’s 99% solved because very rarely it does it but a lot milder.
     
    #9 iceman13, Mar 7, 2020
  10. Max Taiwan

    Max Taiwan Active Member

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    My does the same when I picked it up used at around 40k km. Now at around 60k km. Only at cold start up which I religiously do 1 st thing in the morning. You have to be very attentive to notice it.
    I do not think its coming from the engine. The car nudges when this is happening if you have your hand brake on; the car nudges forward and backwards ever so slightly. And if the hand brake is off you can clearly see the vehicle creeping forwards during this knock. This is only noticeable on static engine start up. I have not felt this with a rolling engine startup(initial) which many people use.
    This was consistent before and after my transmission fluid change.
    My 1st thought was miss fire on start up, but as members reported it was not resolved after coil and spark plug change.
    Regarding feeling slipping transmission... I thought CVT is a slip centered concept. Flooring it will make a big roar and that is about it, for sure there is no dynoing the performance like a DSG or a conventional fixed ratio gear box.
    It will be interesting to get to the bottom of it!
    I am guessing it is a running self diagnosis protocol which checks for something when the engine initiates after a on off cycle of the ECU.
     
    #10 Max Taiwan, Mar 16, 2020
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