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P0300 Misfire - Bad Headgasket?!

Discussion in 'Gen 3 Prius Technical Discussion' started by Sdolla86, Aug 11, 2024.

  1. Sdolla86

    Sdolla86 New Member

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    Vehicle:
    2013 Prius c
    Model:
    III
    Hi All,

    Posting here to get some opinions.

    I have 2013 with 160k miles and got a misfire code. The car has a rough idle but runs fine at higher RPM (1.5k+). No smoke or leaks. Took apart the Egr valve, cooler and intake manifold and cleaned everything (probably could have done a better job for the intake manifold). No change in performance.

    Changed the spark plugs after and didn’t see an improvement. I did a compression test and all four cylinders were between 155-165. I understand I can still do a leak down test but my oil and coolant both look fine.

    I’ll probably buy the coil packs soon - just wanted to get some thoughts here ? Could some of the passages be clogged on the intake?
     
    #1 Sdolla86, Aug 11, 2024
  2. Mendel Leisk

    Mendel Leisk Senior Member

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    Vehicle:
    2010 Prius
    Model:
    Touring
    Always, or in particular with cold starts, then it smooths out?

    Coolant level in reservoir not dropping?

    I’d hold off on any more plug/coil replacements.
     
    #2 Mendel Leisk, Aug 12, 2024
    Last edited: Aug 12, 2024
  3. Tombukt2

    Tombukt2 Senior Member

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    Base
    You're heading to engine dismantling You might want to hold up on firing the parts cannon many have done this here and you can read all about it The parts cannon is usually not a thing to be firing especially with this model there's too many things to go really wrong
     
    #3 Tombukt2, Aug 12, 2024
  4. Sdolla86

    Sdolla86 New Member

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    Aug 11, 2024
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    Location:
    Miami
    Vehicle:
    2013 Prius c
    Model:
    III
    So I ended up changing the coil packs and no change in performance.

    I’ve gotten a little more familiar here and noticed the misfire happens during cold start and when the engine powers on during very low engine RPM <1500 then goes away.

    At this point I gotta think HG. Any sure way to tell it’s going? Would hate to open this engine up to see it’s something else.
     
    #4 Sdolla86, Aug 20, 2024 at 7:04 PM
  5. MAX2

    MAX2 Junior Member

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    Third Rock from the Sun
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    2007 Prius
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    Engine operation depends on many factors, fuel, air, electrics, spark plugs, etc.
    It is necessary to remove the parameters of the systems operation.
    You can use the OBDII scanner and programs.
    Or a laptop with Techstream.
    No more errors appear?
     
    #5 MAX2, Aug 23, 2024 at 3:19 AM
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