engine stumbling/running rough while cruising

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by mattbatson, Sep 19, 2020.

  1. mattbatson

    mattbatson Member

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    my girlfriends 2010...

    about 8 months ago I did the egr clean on her 230k mile car

    a month ago I was driving it through town and thought I could sense a small amount of rough/misfire type behavior from the motor.

    But I rarely drive it...so dismissed it.

    a week ago she is driving to see me and it starts running rough... enough for her to notice.

    I decide to seafoam the car by injecting the spray directly into the intake manifold.

    Car runs great for a few days then begins to stumble again. Then the yellow triangle light comes on.

    She takes it to the dealer as I'm out of town and they say that the car was due for a software update and that is probably the cause of the problem and she gets out of there without spending a dime.

    Next day the car is running rough again.

    No idea if a code was thrown...if so it was erased at dealer.

    Any ideas?

    thanks
     
  2. Raytheeagle

    Raytheeagle Senior Member

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    How's the engine coolant level?
     
  3. mattbatson

    mattbatson Member

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    All good with all the levels I’ve been maintaining it for the last year change the PCV valve, etc. Cleaned the MAF about nine months ago etc. pretty sure I change the spark plugs and a few things like that about a year ago also

    Thanks!
     
  4. bisco

    bisco cookie crumbler

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    you're going to have to read the codes next time the triangle appears.

    did you clean the whole egr circuit?
     
  5. mattbatson

    mattbatson Member

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    I'm out of town and she is on her own for now

    so I could not read anything and she did not get the codes

    I did clean the entire egr circuit...not just the pipe.

    Pretty sure it was the first time the cooler had been cleaned...at 230k miles...and it was mostly clogged...although it was not completly


    this was about a year ago.


    problem cropped up in last couple of weeks
     
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  6. Raytheeagle

    Raytheeagle Senior Member

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    You are sure the coolant level is stable?
     
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  7. mattbatson

    mattbatson Member

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    Yes

    It was the first thing I checked before spraying in the seafoam

    Immediately I suspected blown head gasket

    So update: She texts to say she is put another 150 miles on the car since it ran rough after leaving the dealer and it seems to be running fine now

    I will update again after a few more days as she is headed to VA (about 5 hours)

    Thanks!
     
  8. bisco

    bisco cookie crumbler

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    bad gas?
     
  9. mattbatson

    mattbatson Member

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    It’s possible of course...

    But in all my years with all the cars I’ve owned... I’ve never had a troubleshoot that involved bad gas

    Doesn’t mean it can’t happen

    But the 3rd gen has so many instances of rough running ...

    But hopefully you are correct and this is what caused it and it’s gone
     
  10. fotomoto

    fotomoto Senior Member

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    I'm leaning to a HG beginning to fail. I would do a plug and cylinder check for evidence. If none, then maybe one of the COP's is going bad (fingers crossed). Check for codes. Check the oil condition/level. I would stop driving the vehicle, especially long distances, till resolved.

    GOOD LUCK!
     
    #10 fotomoto, Sep 21, 2020
    Last edited: Sep 21, 2020
  11. jzchen

    jzchen Senior Member

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    Is it possible some residual in EGR (never done this cleaning) plugged it temporarily and now cleared.

    moto g(7) power ?
     
  12. Mendel Leisk

    Mendel Leisk Senior Member

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    230k miles without an EGR
    Sorry, what's a COP? Coil?
     
  13. fotomoto

    fotomoto Senior Member

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    Coil On Plug. I think the acronym was invented for us, umm, experienced folks who would go looking for coils in others places. LOL
     
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  14. jzchen

    jzchen Senior Member

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    Okay, now I get the story after rereading. So the dealer reflashed an ECU and it ran rough because it was (re)adapting. Car is now fine, problem solved as dealer expected...

    moto g(7) power ?
     
  15. Mendel Leisk

    Mendel Leisk Senior Member

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  16. mattbatson

    mattbatson Member

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    Hey

    no ...it was running rough and that is why she took it to the dealer

    That and the yellow triangle
     
  17. mattbatson

    mattbatson Member

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    I suspected as a possibility coil on plug... but from my experience when they go they just go

    and the situation does not get better

    if it starts running rough again though I can check that ....actually have a spare coil on plug in my toolbox
     
  18. mattbatson

    mattbatson Member

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    I really doubt that... it was at least nine or 10 months ago

    Plus to be honest if there was any residual garbage in the cooler I’m pretty sure it would just blow right out the motor and not cause the engine to stumble for a day or two
     
  19. mattbatson

    mattbatson Member

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    Thanks

    I will definitely keep an eye on the oil so far it has looked fine

    I’ve considered doing a compression check
     
  20. Mendel Leisk

    Mendel Leisk Senior Member

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    Leak-down test will be more revealing.
     
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