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Engine knocking at start up... Did not complete warmup cycle the previous night

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Roger T, Dec 30, 2014.

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  1. hlunde

    hlunde Member

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    2010 Prius
    Model:
    III
    Yes, it's normal, because:

    1. Prius is just a Scion with an advanced drive train. After investing in the drive train, there's not a lot left in the cost and weight budgets to install sound deadening.
    2. Driver has no control over engine speed and load. When accelerating, the HSD tends to run the engine under heavy load (near open-throttle to minimize pumping losses) and at moderate rpm to reduce frictional losses.

    Enjoy what the vehicle provides -- superb fuel economy, a spacious interior and high reliability.
     
    #41 hlunde, Jan 15, 2015
    Last edited: Jan 15, 2015
  2. Roger T

    Roger T Member

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    No i am not the one who is driving it
     
    #42 Roger T, Jan 15, 2015
  3. Mendel Leisk

    Mendel Leisk Senior Member

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    Vehicle:
    2010 Prius
    Model:
    Touring
    If you've driven two different years, and the newer one's distinctly quieter, it could be the engineers have recognized some deficit, and made some change. Could also be machining tolerances: both cars are within tolerance limits, but the newer car is just closer. Or some misaligned or loose fasteners peripheral to the engine, say in the intake or exhaust.

    Or due to more miles on the older car: something starting to "go south", like build-up in the Exhaust Gas Recirculation circuit, or exhaust circuit starting to rust?
     
    #43 Mendel Leisk, Jan 15, 2015
  4. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
    Staff Member

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    OK. Let's see if we can get to the heart of the matter.
    Your engine MIGHT be loud if:
    • Your battery state of charge (SoC) is low at the time. This is because the engine will be working to propel the car and recharge the battery, both at the same time.
    • You just started the car and within one minute are driving at speeds greater than ~30 mph. For example, leaving work in the evening. This is because during the warm-up cycle, the Prius is being propelled primarily by battery power and the engine can run hard to complete the warm-up cycle. Consequently, if you run the battery low during this time, you will transition into the first bullet.
    • It's very cold outside and you have the heater running.
    • There is physically something wrong with your car.
    Because of the continuously variable transmission (CVT) the engine can run loud at times. This, in and of itself, it not a bad thing; it's just how it goes. Unfortunately, you are the only one here who has actually heard the sound so we can't judge whether it's a normal loud sound or an abnormal loud sound.
     
    #44 TonyPSchaefer, Jan 15, 2015
  5. bisco

    bisco cookie crumbler

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    perhaps there is a hole in the exhaust system?
     
    #45 bisco, Jan 15, 2015
  6. butchbs1985

    butchbs1985 Taking things apart is fun!

    Joined:
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    Location:
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    Vehicle:
    2013 Prius v wagon
    Model:
    Three
    So obviously the knock issue hasn't been corrected since release of the TSB. Has anyone with a newer Prius gotten anywhere with a dealer? I can pretty much make my 2013 Prius V do it any time I wish. It sounds absolutely horrible. I'm to the point that if I move the vehicle out of the garage to the driveway or shuffle it around to clear snow, I leave it running so it warms up. I'd rather waste the fuel than have another episode of whatever horrific thing is going on under the hood happen.

    I'd love to take it to the dealer and have them look at it but am nearly certain it'd be time wasted.
     
    #46 butchbs1985, Jan 18, 2015
  7. bisco

    bisco cookie crumbler

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    don't bother.:sick:
     
    #47 bisco, Jan 18, 2015
  8. Tande

    Tande Active Member

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    It's ONLY a TOYOTA FGS!.......:giggle:
     
    #48 Tande, Jan 18, 2015
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