2015 Prius V engine shaking when starting in the morning

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by Nye, Nov 7, 2024.

  1. Nye

    Nye New Member

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    My daughter has informed me that her 2015 Prius V has been making a strange shaking rattling noise when starting in the morning. Recently, I replaced the spark plugs after receiving a misfire code for cylinder 4 (P0304), but I didn’t replace the ignition coils at that time. Since then, the check engine light has not come back on, but this noise recently started?
    The car has about 195,000 miles on it, mostly highway driving. My question is whether I should replace all the ignition coils or just start by replacing the one on cylinder 4.
    Also, could anyone recommend a good brand for long-lasting coils? I’ve seen Denso recommended, but they are not cheap.
    I'm a bit concerned after reading forums where this issue seems common in Priuses, and some owners have faced costly repairs. I'm hoping to avoid going down that path if possible, so any advice would be greatly appreciated!
    Thanks in advance for your help.
     
    #1 Nye, Nov 7, 2024
  2. rjparker

    rjparker Tu Humilde Sirviente

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    If it clears up and runs fine after the cold start, you need to check for a head gasket leak that has those exact symptoms. A borescope is the only reliable method in early stages.

    Waiting until you have large coolant losses or white smoke can cost you the engine.


    Car Care Nut HG Borescope at 7:40
     
    #2 rjparker, Nov 7, 2024
    Xterra72, Leadfoot J. McCoalroller, Nye and 1 other person like this.
  3. Carall

    Carall Member

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    #3 Carall, Nov 10, 2024
  4. Mendel Leisk

    Mendel Leisk Witness Leader

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    Fugedabout plugs and coils; it’s head gasket failure. If you stick with it be sure to clean the EGR system too, including the EGR passages in intake manifold.

    first 2 links in my signature relate to EGR cleaning, last is full engine section form repair manual. On a phone turn it landscape to see signatures.
     
    #4 Mendel Leisk, Nov 10, 2024
  5. Nye

    Nye New Member

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    The strange part is, after using B12 fuel injector cleaner, the shaking has stopped in the morning. I've been checking it daily in the mornings, and it's been starting fine. However, my daughter says it's happening later in the day, like after school or today when she volunteered for four hours. Could this still be a head gasket issue, or does it sound more like the EGR valve? I was hopeful that the problem was resolved, but now it seems to happen midday instead of in the mornings.
     
    #5 Nye, Nov 11, 2024
  6. rjparker

    rjparker Tu Humilde Sirviente

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    An egr system won’t cause the severe stumbling and rattling of a hg leak. It might stick open at idle causing a slightly rough engine. There is a simple egr tube blocking technique to completely eliminate the egr.

    Car care Nut Egr video with block tube test


    An early stage hg leak depends on a fully warmed up engine pressurizing the coolant system prior to shutdown. This pressure pushes a few drops of coolant into the cylinder over a few hours causing the extreme rattling caused by temporary misfires. Sometimes it does not happen; likely due to valve state at shutdown.

    A borescope test is needed.
     
    #6 rjparker, Nov 11, 2024
  7. Mendel Leisk

    Mendel Leisk Witness Leader

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    It's both, a cascade effect. Long neglect of the (poorly designed and insufficiently tested) 3rd Gen EGR system leads to carbon clogging, and to unevenly supplied (cylinder one typically starved first) and overly hot exhaust gas, engine overheats (unevenly), and head gasket succumbs.
     
    #7 Mendel Leisk, Nov 12, 2024
  8. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Do a borescope check soon. If you catch it early enough you can get out of it with just a gasket job.

    If left a while the next cheapest cure is a replacement engine.
     
    #8 Leadfoot J. McCoalroller, Nov 12, 2024
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