Misfire on all cylinders

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Matt98svt, May 21, 2026 at 11:17 AM.

  1. Matt98svt

    Matt98svt Junior Member

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    Wife has a 2012 Prius and was starting out on a trip this morning. Made it 10 miles and car started to shudder all the sudden so she pulled over. Codes are showing misfire on all cylinders randomly. Starts fine will idol but with constant misfires and shudders harder if you hit the gas. No coolant loss. Head gasket replaced 20k ago as well as EGR cleaned, new pvc valve, new plugs etc. the only thing I can think of is I removed the very back heat shield that’s underneath the car last night as it was coming loose but looking under the car I don’t see any dripping fuel or anything damaged wires etc. any thoughts on what it might be?
     
    #1 Matt98svt, May 21, 2026 at 11:17 AM
  2. bisco

    bisco cookie crumbler

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    bad gas?
     
    #2 bisco, May 21, 2026 at 1:47 PM
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  3. CR94

    CR94 Senior Member

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    Check for vacuum leaks if a hose is off or cracked? Those symptoms may resemble those of a malfunctioning fuel vapor-recovery valve.
     
    #3 CR94, May 22, 2026 at 12:36 AM
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  4. Mendel Leisk

    Mendel Leisk MMX GEN III

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    What’s the miles?
    Who did the head gasket replacement?
    Who cleaned the EGR system?
     
    #4 Mendel Leisk, May 22, 2026 at 9:17 AM
  5. shawn.ne

    shawn.ne Member

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    This may be a little off topic, but if the misfire was just on one cylinder is it possible to disable just that cylinder? If the misfire was due to something that would normally require a replacement engine, maybe this could be an emergency fix. When I was younger I once owned an '83 Tercel that was running on 3 out of 4 cylinders, and I drove it like that for about a year. I never worked on my cars in those days so I don't know why that one cylinder wasn't working.
     
    #5 shawn.ne, May 25, 2026 at 10:58 PM
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