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Random Misfire On All Cylinders

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by anima immortale, Apr 23, 2017.

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  1. anima immortale

    anima immortale New Member

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    2007 Prius
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    I have an 07 Prius Base with ~156K miles. The check engine light came on and reading the codes shows a P0300, 301, 302, 303, and 304. It is running extremely rough due to the misfires.

    I replaced the 12V because the voltage reading was around 11V, so slightly out of spec. I replaced the spark plugs as they were extremely corroded. There was a little oil on the plug threads and crush ring, none on the tips. It ran fine for about a week after replacing the plugs then started misfiring again.

    At this point I took it to the dealer. They noticed the oil on spark plugs as well (about 3 weeks out from replacing the plugs). They said there were no other issues and that they would need to dig in to the engine to determine the cause of the oil leak. This would be at a cost of $2800+. Not worth it for this car. Again, the car ran fine for a week after the dealer cleaned the plugs.

    What could cause an oil leak on all four cylinders? My first suspect is the valve cover gasket but the boot and insulator look fine. Also, would an oil leak from that cause aggressive misfire?

    Is it possible that the oil leak and misfire are unrelated?
     
    #1 anima immortale, Apr 23, 2017
  2. windstrings

    windstrings Certified Prius Breeder

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    Does it misfire upon starting or after its been running or all the time?

    SM-N910V ?
     
    #2 windstrings, Apr 23, 2017
  3. Sandollars

    Sandollars Prius Maven

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    Sounds like the stealer is trying to stick it to you...

    An '07 Prius engine with less than 60k miles can be purchased for 800-1200 bucks and installed for 500. Do an internet search.
     
    #3 Sandollars, Apr 23, 2017
  4. anima immortale

    anima immortale New Member

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    It misfires on startup and while idling.
     
    #4 anima immortale, Apr 24, 2017
  5. anima immortale

    anima immortale New Member

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    Yeah, that's why I didn't have them fix it. I'm wondering if this is likely a simple fix like the valve cover gasket or if it is more extensive like the cylinder rings. I don't really have any investment in this car other than it is paid off so to drop a new engine in it doesn't really make sense to me.
     
    #5 anima immortale, Apr 24, 2017
  6. andrewclaus

    andrewclaus Active Member

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    A leaking valve cover gasket could explain oil on the spark plug threads, but it should not cause the misfires unless oil was fouling the COPs (coils on plugs). You say those look clean?

    Do you know if the "extremely corroded" plugs were original? Where was the corrosion?

    You may want to do a compression or leak-down test. To do a compression test, you'll need Mini VCI with Techstream (about $20, running on an old 32-bit laptop) to spin the engine.

    How much oil does the engine consume?

    Also, are you using a Prius-specific scanner (like the Mini VCI)? If not, you might be missing some codes.
     
    #6 andrewclaus, Apr 24, 2017
  7. Priusprofit

    Priusprofit Member

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    Did you end up resolving this issue? I am experiencing the identical situation

    Posted via the PriusChat mobile app.
     
    #7 Priusprofit, Jan 17, 2019
  8. windstrings

    windstrings Certified Prius Breeder

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    Usually this only happens after it's been sitting a long time "days"... A sort of vapor lock.
    Usually simply killing the engine and restarting ends it.

    There is no documented harm that happens from this anomaly.
     
    #8 windstrings, Jan 17, 2019
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