Help: 2019 prius 155k - 1-2 second shake when starting up

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by franksrental, Jan 5, 2026 at 9:28 PM.

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  1. franksrental

    franksrental Junior Member

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    Hi everyone,

    I recently drove my father's Prius for the first time in over a year and noticed the car shakes or rattles slightly during every startup.

    For context, I own a Gen 3 Prius that I purchased used, and I had to replace the engine due to the infamous 'rattle of death'/EGR problem. Now I'm wondering if my dad's car is experiencing the same issue. From what I've read, Gen 4 models aren't supposed to have this problem—or at least it's very uncommon. His car only has 155k miles on it, though I should mention the maintenance history has been poor: the spark plugs still haven't been changed, oil changes happen every 15k+ miles, and I'm not sure what else has been neglected.

    I'd really appreciate any insight you can offer! Of course, I'm trying to convince my father that regular maintenance is essential, but getting him to listen is another story.

    Thanks in advance for your help!
     
    #1 franksrental, Jan 5, 2026 at 9:28 PM
  2. franksrental

    franksrental Junior Member

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    forgot to mention that the coolant level was at the minimum so there has been some leaking. thanks again for reading! Also I read about the possible catalythic converter leak besides the head gasket issue...
     
    #2 franksrental, Jan 6, 2026 at 11:30 AM
  3. bisco

    bisco cookie crumbler

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    if the coolant hasn't been changed yet, it could be a normal level for 155k.

    ifit were mine, i would do all the standard maintenance for time and miles, and throw in engine items that aren't on the list, like throttle body cleaning.

    if it is still rattling, then a head gasket check is appropriate. you can find methods on youtube, like boroscope.
    top up the coolant, and keep an eye on it.
     
    #3 bisco, Jan 6, 2026 at 1:47 PM
  4. franksrental

    franksrental Junior Member

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    thanks so much bisco, so worst case it could be the head gasket even with 155k and 6 year old?
     
    #4 franksrental, Jan 6, 2026 at 10:10 PM
  5. bisco

    bisco cookie crumbler

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    any car with 155k is a possible head gasket issue, but unlikely
     
    #5 bisco, Jan 7, 2026 at 1:37 PM
  6. BiomedO1

    BiomedO1 Senior Member

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    Get all the maintenance up to date and change both coolants. Pay special attention to the old spark plug condition and keep track of where each plug comes from. Post pictures of the ends of each plugs.
    It may just be condensation in the combustion chamber, but 15K mile oil changes is really pushing it - especially if you use cheap oil. IMHO.
    Get that coolant level topped off right away, because that's a sure way to blow a head gasket - since the dummy lamp doesn't go off until 285+F, NO beeps or alarms; you just need to notice it lit!!!
     
    #6 BiomedO1, Jan 7, 2026 at 1:50 PM
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