2012 III- Engine shake and rattle

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by edster, Jun 5, 2026 at 10:23 AM.

  1. edster

    edster Junior Member

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    Hello, My 2012 III has 230k, regularly maintained. At start, the engine rattles and shakes. This happened a few times since new, eventually smoothed out but didn’t last. Check engine lite on this time. Any clues? I don’t know if it can make it safely a quarter of a mile away to get it read from Autozone. Am afraid the engine may be conking out.
    Thanks for any input.
    Ed
     
    #1 edster, Jun 5, 2026 at 10:23 AM
    bisco likes this.
  2. bisco

    bisco cookie crumbler

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    most likely a blown head gasket, very common on gen 3. you're okay to drive there, but make sure the coolant is full.
    if it clatters too much, shut down and try again
     
    #2 bisco, Jun 5, 2026 at 2:15 PM
  3. edster

    edster Junior Member

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    Hi again,
    I finally took it to Autozone to get scanned. The report is as generic as it can be.
    Code P0300
    Random/ Multiple Cylinder Misfire detected.
    Cylinders 1-3.

    That’s about it. So you really sure it’s the head gasket? I’m willing to get it fixed to a certain dollar amount. The car is in good condition otherwise.
    Thank you!
     
    #3 edster, Jun 9, 2026 at 7:24 PM
  4. edster

    edster Junior Member

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    By the way, don’t know if I mentioned this. All fluids seem fine. I kept reading about coolant issues. There’s more than enough, no leaks whatsoever.
     
    #4 edster, Jun 9, 2026 at 7:30 PM
  5. Mendel Leisk

    Mendel Leisk MMX GEN III

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    So probable codes P0301 and P0303 as well (indicates misfires on cyl's one and three). Considering the miles and cylinders, sounds like it's advanced head gasket failure.

    If you stick with it ensure the EGR (Exhaust Gas Recirculation) system, including intake manifold EGR passages, is thoroughly cleaned. With those miles the EGR cooler should maybe just be replaced, it's interior will be badly clogged.

    There's some relevant links in my signature (on a phone turn it landscape to see signatures)
     
    #5 Mendel Leisk, Jun 10, 2026 at 1:27 PM
  6. rjparker

    rjparker Tu Humilde Sirviente

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    #6 rjparker, Jun 10, 2026 at 2:03 PM
  7. ASRDogman

    ASRDogman Senior Member

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    Have you checked the wiring?
    Have you swopped the plugs to see if the missfires changed cylinders?
    Have you swopped the coils to see if the misfires changed cylinders?

     
    #7 ASRDogman, Jun 10, 2026 at 3:01 PM
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