Missfire Cylinder 4

Discussion in 'Gen 3 Prius Main Forum' started by gjkristi, Dec 16, 2025 at 9:34 AM.

  1. gjkristi

    gjkristi Junior Member

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    I have a 2010 Prius and I'm getting a check engine with Cylinder 4 missfire. Head gasket has been replaced and the engine never goes down so don't think it's that. I replaced the EGR (with toyota new) cleaned the intake and all the pipes. Replaced the spark plugs with new one step hotter plug. Swapped coils 3 and 4. Never see a missfire driving but after a couple weeks check engine light comes on. Anything to try next?
     
    #1 gjkristi, Dec 16, 2025 at 9:34 AM
  2. BiomedO1

    BiomedO1 Senior Member

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    does the problem ever move off of #4?
     
    #2 BiomedO1, Dec 16, 2025 at 10:30 AM
  3. gjkristi

    gjkristi Junior Member

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    No it does not move from #4
     
    #3 gjkristi, Dec 16, 2025 at 12:54 PM
  4. ASRDogman

    ASRDogman Senior Member

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    Switch the #3 an 4 coils. If the problem stays at 4, switch the coils back,
    and switch the spark plugs.
    If it changes, it's the plug.
    Are the plugs from Toyota? Or ebay/amazon..... cheap chinese copies.

    Also, check the wiring harness. It's easy to mess something up without realizing it....

     
    #4 ASRDogman, Dec 16, 2025 at 1:51 PM
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