Mild acceleration "shudder"

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by PriusPaddler, Dec 4, 2024.

  1. PriusPaddler

    PriusPaddler Member

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    My 2009 baby with 333,333 miles on it, recently replaced spark plugs and solved P0301/P0300 issues.

    That also seemed to improve or solve the rough idling and codes have not returned.

    For years, I gave driven with P0420 for catalyric converter (I assume). Long ago I replaced one of the oxygen sensors but the 420 code remained and I just kept driving.

    Now, about a month after spark plug replacement, the car is hesitating or shuddering when accelerating slowly. So any speed under 45mph, or if trying to increase slightly, at 60mph or so. Cruising is fine, coasting is fine, sharp acceleration is mostly fine...

    Occurs just when pressing gas pedal.

    There are no new codes. P0420 only.

    Is it time to finally replace that cat? Or might I have something else going on?

    A brief search showed someone else had similar symptoms and it was oil in crankshaft??

    I do burn oil. Maybe something less than a quart in 3k miles.
     
    #1 PriusPaddler, Dec 4, 2024
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  2. JC91006

    JC91006 Senior Member

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    These cars often have fuel injector problems when the mileage gets higher. The would explain the misfire codes and the hesitation in acceleration.

    Also it's a good idea to clean out the throttle body while you're doing maintenance.
     
    #2 JC91006, Dec 4, 2024
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  3. PriusPaddler

    PriusPaddler Member

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    Would that be true if no longer throwing a misfire code?

    Only code is the P0420...
     
    #3 PriusPaddler, Dec 4, 2024
  4. BiomedO1

    BiomedO1 Senior Member

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    The new plugs are simply masking an old problem. If you use a proper scan tool, you would see that your problem still exist, just not consistent enough yet to set a code. A proper scan tool will also allow you to nail down the P0420 code, instead of pointing a parts cannon at the car. IMHO
     
    #4 BiomedO1, Dec 4, 2024
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  5. saneesh8

    saneesh8 Junior Member

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    My bmw z3 2.5L had the same. No error codes and in rare cases it used to shutdown also. Put new plugs in, same. Finally it threw the code and it was one of the coils. Replaced it and no issues after that. Had ~148k on it.
     
    #5 saneesh8, Dec 4, 2024
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  6. BiomedO1

    BiomedO1 Senior Member

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    I had a similar issue with my GMC truck. I could feel the intermittent miss on steep climbs, but the ECU never flagged it for about 18 months. It just came back as a pending P0300. Couldn't troubleshoot because it was so intermittent - finally became less intermittent, so I could troubleshoot it around 220K.
     
    #6 BiomedO1, Dec 4, 2024
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  7. PriusPaddler

    PriusPaddler Member

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    Maybe i need to ask Santa for a better scanner :)
     
    #7 PriusPaddler, Dec 4, 2024
  8. mr_guy_mann

    mr_guy_mann Senior Member

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    What brand of spark plugs and where did you get them? There are problems with counterfeit parts on the web.

    How old are the coils? Might consider getting a new set as "periodic maintenance".

    Your symptoms could be the early stages of ignition problems. I see more ignition faults than injector faults. (You could look at short & long term fuel trim numbers in ECM data while idling and driving. Ideally short + long trims would stay at 0 +/- 10% under all conditions).

    Personally I use NGK plugs and Denso or Toyota (Denso) coils from a reputable source.

    Here's a thread that reviews several scantool apps and devices for smartphones.

    https://priuschat.com/index.php?posts/3246758

    Posted via the PriusChat mobile app.
     
    #8 mr_guy_mann, Dec 5, 2024
    Last edited: Dec 5, 2024
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  9. saneesh8

    saneesh8 Junior Member

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    Regarding "counterfeit parts on the web", i was a victim of this. Buy only from reputed online stores/sellers.
     
    #9 saneesh8, Dec 5, 2024
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  10. PriusPaddler

    PriusPaddler Member

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    Thanks I was headed here to search for that tonight.

    I have one of the recommended cheap ODB2 devices and use the free Torque and Dr. Prius apps now. Will see what else I can afford or get Santa to buy.
     
    #10 PriusPaddler, Dec 5, 2024
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