1. Attachments are working again! Check out this thread for more details and to report any other bugs.

new plugs...now misfiring on cyl 2&4, and far from home

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Lyle Ryan, Mar 5, 2022.

  1. Lyle Ryan

    Lyle Ryan Junior Member

    Joined:
    Jun 27, 2012
    27
    5
    0
    Vehicle:
    2010 Prius
    Model:
    II
    My 2010 Prius has 210K miles on it. For some time, it would give the classic knock/misfire on startup, but only on the first start after 2 to 4 weeks of sitting idle. A little coolant and a quart or two of oil were usually consumed between 10K dealer service.

    I had the dealer install new plugs about 500mi ago, and now it's misfiring for 5-10sec seemingly every time the engine starts, and maybe even when the engine activates in the middle of driving.

    OBD cods are 300, 302, and 304 (cylinders 2 & 4 misfiring). The "check engine" light is on but not flashing.
    I'd suspect the head gasket is going or the EGR system problems are finally catching up with me, but the misfires got dramatically worse just 500mi after the new plugs.

    I have a service appointment in a few days, but am 500 miles from home and the dealer. I'm tempted to limp home to the dealer. If the check light starts flashing, I'll stop & get a tow to a dealer along the route.

    Any opinions on whether it's foolish or reasonable to try to make it home to my dealer?
    I suppose another option is to have a local dealer look at it before I make the trip, but at least I trust my guys at home (haha).
    Thanks....
     
  2. drbtz

    drbtz Member

    Joined:
    Feb 11, 2021
    102
    51
    1
    Location:
    United States
    Vehicle:
    2015 Prius
    Model:
    III
    The coolant is definitely concerning and reason to believe your head gasket is going. To be frank it would probably be foolish to drive home. Many people have driven many miles on bad gaskets but many people have also thrown rods from driving in bad head gaskets too.

    Ultimately it's your call. If it were me I wouldn't drive it.
     
  3. Lyle Ryan

    Lyle Ryan Junior Member

    Joined:
    Jun 27, 2012
    27
    5
    0
    Vehicle:
    2010 Prius
    Model:
    II
    Thanks. That's all I was looking for...an opinion and more info. I'll decide, and take responsibility for it.
    It's Sunday, so the plan is to call my home dealer and the local dealer on Monday morning, and see what they say.
    Wouldn't a head gasket failing on non-adjacent cylinders be a bit unexpected though?
     
  4. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

    Joined:
    May 12, 2018
    6,690
    6,379
    1
    Location:
    Pennsylvania
    Vehicle:
    2018 Prius c
    Model:
    Two
    Head gasket leaks arrive in different forms, generally leaking combustion pressure to (something else.) The three most common are from combustion to coolant, combustion to oil galley, or from one combustion chamber to another.

    You seem to be assuming that last mode of failure, yet you've also reported coolant loss which is more strongly associated with a combustion to coolant breach.

    Might even have more than one going in there.

    I would not have expected new spark plugs to have suddenly changed this problem. Possibly wrong type used?
     
    drbtz likes this.