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Rattling noise from engine under acceleration

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by CK9887, Oct 31, 2023.

  1. CK9887

    CK9887 Junior Member

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    2016 Prius with 92K miles. Purchased used a year ago so not sure what maintenance has been done.

    I’ve noticed what sounds like a rattling sound coming from the engine under acceleration, which goes away after a few seconds once the car gets moving. It’s more prevalent from a stand still, I’m guessing because the engine is under a heavier load. It seems like it has become more noticeable over the last few months.

    It doesn’t seem to be causing any driveability issues and MPG has been consistent at 54mpg. At this point, it seems to be just audible, I don’t feel any vibrations or shaking although audibly it sounds like a vibration/rattle.

    My first suspicion is the EGR valve? Are these symptoms consistent with that? I know it was a common issue on the Gen3, but what about the Gen 4’s?

    Thanks
     
    #1 CK9887, Oct 31, 2023
    Last edited: Oct 31, 2023
  2. bisco

    bisco cookie crumbler

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    haven't read about any gen 4 egr issues, they did change the setup a bit.

    how is the coolant level?

    could anything be loose and vibrating?
     
    #2 bisco, Oct 31, 2023
  3. FuelMiser

    FuelMiser Senior Member

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    Yes, the engine will rattle under load. Nothing to worry about.
     
    #3 FuelMiser, Nov 1, 2023
  4. CK9887

    CK9887 Junior Member

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    Interesting. Is this a design flaw? I’ve owned a lot of cars over the years and have never had an engine rattle under a load, unless it was something loose externally in the engine bay. But this definitely sounds internally.
     
    #4 CK9887, Nov 1, 2023
  5. FuelMiser

    FuelMiser Senior Member

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    Sorry, I’ve been MIA since Nov 1; but to answer your question, I don’t think you can suspect a design flaw in cars/engines that run trouble free for 150K+ miles routinely. In general, 4-cylinder engines will make more rattle than other configurations. Plus Prius uses an Atkinson-cycle engine, which is designed for better efficiency over power and maybe this contributes to the rattle. IDK.
     
    #5 FuelMiser, Nov 16, 2023
  6. axle2152

    axle2152 Active Member

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    The only time I have heard anything that I would describe as a rattling sound is at idle when the engine starts cold, but not that I have noticed when taking off accelerating from a stop, light or hard acceleration. Any chance the rattle you're hearing can be picked up on a recording? These cars do make some noises that are unusual compared to other cars so it could be totally normal. I will say that 92k is way early to have engine trouble as these engines are known to be pretty reliable.
     
    #6 axle2152, Nov 18, 2023
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