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Help diagnose a constant cylinder 2 misfire?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by SB6, Oct 5, 2024 at 8:45 AM.

  1. SB6

    SB6 Member

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    2010 Prius II, 182k miles. P0302 since about 3-4 weeks ago.

    I tried swapping spark plug 2 and 3 and clearing the codes to see if it changed from P0302 to P0303, but no luck. Tried the same with coils 2 and 3, and it looked like the same result. I'm going to retry this to confirm.

    I tried blocking off the EGR valve with a metal spatula to see if the misfires smoothed out, but no luck (I think the code turned to P0304 after clearing codes and doing this test, for some reason).

    Engine coolant and oil seemed at normal levels, and not discolored. I haven't noticed any white smoke from the exhaust.

    182k miles now, as mentioned above. Around 140k I did my engine coolant pump, both coolants, PCV valve, spark plugs, and cleaned my intake manifold, throttle body, EGR pipe, and EGR (although I guess I didn't fully clean, just did the best I could and put it back together). No oil catch can. Also did my transmission fluid around the same time, if it matters.

    What tests can I do to see if it's something I can fix on my own, rather than having to fork over $3-5k for having someone replace the engine? Would appreciate some guidance. I'm not the best with cars, but by following videos and instructions, I've gone from screwing up a simple oil change to doing my own brakes, suspension, and "tune up" stuff mentioned above.
     
    #1 SB6, Oct 5, 2024 at 8:45 AM
  2. Tombukt2

    Tombukt2 Senior Member

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    This is normal for this engine and this model Don't get too hung up on it because you can have a lot of money in it no matter who's doing the work Is the car in that nice of a shape to warrant winding up spending 3 to 5K If your time is free well so be it most people's time is not free they have places to be work to do etc so there's always that You're working on something that is pretty much planned obsolescence and executed very well by the likes of a company called Toyota and if you don't think they know how to enact plan obsolescence well you have another thing coming you're sitting in it Go back one year to a 2009 Prius and notice the huge difference in reliability and all of that Just one year it is amazing but a that's where we are anything you can do inexpensively I doubt it You see all the shops popping up around the country just to deal with this issue between 3:00 and 8K is generally what you're looking at Good luck the whole car isn't worth that at least not to me I have two sitting here please come get them
     
    #2 Tombukt2, Oct 5, 2024 at 8:54 AM
  3. Mendel Leisk

    Mendel Leisk Senior Member

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    At 182k miles, with EGR semi-cleaned at 140k miles, and cylinder 2 misfire? Head gasket.

    how’s the oil consumption?
     
    #3 Mendel Leisk, Oct 5, 2024 at 9:21 AM
  4. SB6

    SB6 Member

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    None noticed
     
    #4 SB6, Oct 5, 2024 at 9:26 AM
    Mendel Leisk likes this.
  5. Mendel Leisk

    Mendel Leisk Senior Member

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    You could score the Toyota gasket kit (includes head hasket), new head bolts, a tube of Permatex Ultra-Black and a 10 mm double-hex bit and have at it.

    Do a thorough EGR clean while you’re at it, and consider an oil catch can.

    full disclosure: never done anything like this personally.
     
    #5 Mendel Leisk, Oct 5, 2024 at 9:36 AM
  6. SB6

    SB6 Member

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    Looking around on Google, it looks like I can do a compression test and a leak down test to test for the head gasket. Compression test looks doable for me, although if you have a good video or something for it, please do link it. Haven't looked into the leaks own test yet. I also saw something about getting an exhaust gas test kit for the coolant?
     
    #6 SB6, Oct 5, 2024 at 9:46 AM
  7. rjparker

    rjparker Tu Humilde Sirviente

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    Knowing the symptoms can be useful. Has it shaked and rattled on engine starts only to clear up as it warms up? If so how long ago did this start and how often does it happen now?

    None of that is conclusive on early gen3 head gasket leaks. So much so I would not waste my time on a compression or leak down test.

    A quality dual view borescope is a decent hg verification tool.

    Early leaks are very small and depend on coolant pressure seeping into a cylinder as the engine cools. On a cold start, the plug may be fouled or may not.

    When it’s an advanced hg fail it may shake and rattle after warmup and be noticeable with the coolant gas test. At that point coolant reservoir drops can be observed. Even later white smoke may be observed in the back as the engine is rev’ed. At that point the odds are good a hg alone won’t fix it long term.


    Shudder video
    “Hey Walt… they want to wait and see if it gets worse…”



    Car Care Nut HG Borescope at 7:40
     
    #7 rjparker, Oct 5, 2024 at 10:12 AM
    Last edited: Oct 5, 2024 at 10:27 AM
    Brian1954 and Mendel Leisk like this.
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