2011 178k Misfire and Low Comp on Cylinder 4

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by nyej01, Oct 31, 2020.

  1. nyej01

    nyej01 Junior Member

    Joined:
    Oct 31, 2020
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    Location:
    Ohio
    Vehicle:
    2011 Prius
    Model:
    Three
    Long time lurker, first time poster. I've dug through all the vidyas and I'm at my hail mary point.

    I've spend some real time over the last 2-3 weeks tearing into this guy. Bought at 50k now at 178k, minimal maintenance:
    * Front Wheel bearings at 120k
    * Brake pads/Rotors at 120k
    * Regular oil changes at every 10k(Full Synthetic)

    Then kaboom... shaking, rattling and knocking on startup at 178k. When I put some gas to it, she stops knocking and misfires stop, but as soon as it's back to idle the knock is back.

    I have done the following:
    * Manifold/Intake cleanout
    * EGR Pipe Cleanout
    * EGR overnight soak/scrubdown (can see through this baby now, she was plugged something ugly)
    * PCV Valve replacement
    * All new plugs
    * All new Coils

    Compression test shows all cylinders +/-10 psi except Cylinder 4. Cylinder 4 is popping 35psi.... which is 150psi below the others.

    With bad compression in one cylinder, what are my next options before I know it's a head gasket?

    Edit: She's not burning oil or coolant. My oil looks clean.
     
    #1 nyej01, Oct 31, 2020
    Last edited: Oct 31, 2020
  2. pjksr02

    pjksr02 Active Member

    Joined:
    Nov 2, 2009
    532
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    Location:
    Connecticut
    Vehicle:
    2010 Prius
    Model:
    III
    That's a tough one. It sounds like you cleaned everything, but it may have been too late, even though the failure is usually at cylinder 1 (or 2). You could try a head gasket stop-leak product, and hope for the best. Or just give it the gas to avoid knocking. Probably it's not the EGR valve itself.
     
    #2 pjksr02, Oct 31, 2020
  3. jimontheocean

    jimontheocean Member

    Joined:
    Jul 1, 2020
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    Location:
    SC
    Vehicle:
    2010 Prius
    Model:
    Two
    Wow, with compression like that on number 4, I would pull it into my garage and begin tearing it down to the block.

    Posted via the PriusChat mobile app.
     
    #3 jimontheocean, Nov 1, 2020
    Last edited: Nov 1, 2020
    pjksr02 likes this.
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