Misfire woes

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by polophonic, Jan 25, 2025 at 9:26 AM.

  1. polophonic

    polophonic Junior Member

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    Greetings all, I have learnt a huge amount from this forum and in doing so saved many £££$$$. But I now think I have a problem that has stumped me. So if anyone is able to help then I would be very very grateful.

    I have a persistent #1 misfire - P0301 - with also intermittent P0300,/3/4. Having searched the threads, I have done the following with no effect:

    1 - replaced spark plugs (all plugs looked good, there was some corrosion around top of #1 seems the usual issue of water/oil ingress there)

    2 - replaced coil pack #1,

    3 - moved coil packs between cylinders to see if the problem moves

    4 - replaced fuel injectors

    5 - tested compression on all cylinders, they are all a little under 125 (after repeating the test)

    The particular symptoms I experience, is that the car runs smoothly with no load (e.g. in park put foot on gas pedal), but the moment its charges up the hybrid battery, very loud clunking and shaking starts. Driving can produce a blinking engine management light.

    Could this a be a bearings, rods, bottom end problem, and if so what would be my next steps for diagnosis?

    Many thanks!
     
    #1 polophonic, Jan 25, 2025 at 9:26 AM
  2. Tombukt2

    Tombukt2 Senior Member

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    No coolant disappearing You've ruled out a head gasket You've replaced the coil that you thought could be the offending one which I'm guessing is cylinder one and then you moved the cylinder one coil to another cylinder and put that cylinder in one and nothing changed we're still misfiring on cylinder one? And all your compression is about 125 which isn't too awfully horrible for a near 20-year-old engine I don't think.
     
    #2 Tombukt2, Jan 25, 2025 at 6:11 PM
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  3. mr_guy_mann

    mr_guy_mann Senior Member

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    Typically, nothing in the cylinder block is going to be variable. Either it works, or it's broken.

    While it is possible to have something like a broken valve spring (that might be RPM sensitive), most top end mechanical faults are constant (always broken). Not load sensitive.

    You have done fairly comprehensive "swap-tronics" to rule out the most common faults.

    Unfortunately the next level of diagnostics requires some sophisticated equipment like digital oscilloscopes, and the knowledge to use them (or interpret advanced scantool data , vacuum gauge readings, testing ignition coil output, etc.)


    Posted via the PriusChat mobile app.
     
    #3 mr_guy_mann, Jan 25, 2025 at 9:25 PM
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  4. MAX2

    MAX2 Member

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    #4 MAX2, Jan 26, 2025 at 12:06 AM
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  5. polophonic

    polophonic Junior Member

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    Many thanks for reply - yep, that about covers it and what I have concluded. Looks like I have a bit more complex problem determination to get to grips with.
     
    #5 polophonic, Jan 26, 2025 at 7:40 AM
  6. polophonic

    polophonic Junior Member

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    Many thanks - I will see if costs of kit makes it sensible to go that route, or whether I should continue to try and find a competent and reasonably priced garage to take a look.
     
    #6 polophonic, Jan 26, 2025 at 7:41 AM
  7. polophonic

    polophonic Junior Member

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    #7 polophonic, Jan 26, 2025 at 7:41 AM
  8. pasadena_commut

    pasadena_commut Senior Member

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    Really, no P0302? Ever? If that's really the case it sounds like a timing problem of some sort, which hits 1 a lot, 2 never, and 3,4 intermittently. Hard to imagine any general problem (like fuel pressure or a MAF issue) with that sort of specificity.
     
    #8 pasadena_commut, Jan 26, 2025 at 2:49 PM
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