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Strange engine braking behavior, Prius 2009

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Louis Horvath, Sep 6, 2024 at 8:58 PM.

  1. Louis Horvath

    Louis Horvath Junior Member

    Joined:
    Aug 9, 2022
    40
    9
    1
    Location:
    Prevost, Quebec, Canada
    Vehicle:
    2005 Prius
    Model:
    Base
    I'll make this simple.
    Had a 2005 Prius I loved. Sadly after 260k miles the engine just shakes and shakes even if I changed the spark plugs and coils. Car is worth less than a tow to my mechanic :(

    SO I BOUGHT A USED PRIUS 2009.
    Works great but I'm having a strange issue.
    I use engine braking a lot. Never had any issue with my Prius 2005.

    On the 2009, when I use the engine break it suddenly cuts loose at about 6-12 miles per hour, even on flat terrain.
    That is I have to press on the break or else it's as if the engine break has "let go".
    Same feeling when the car uses the ABS but there's no ABS light. To be clear, I'm not using the break pedal UNTIL the engine break lets go.

    There's no codes, no lights on the dashboard.

    Is this expected behavior for a 2009?

    Full disclosure, I brought the car to my local mechanic (that I trust completely) because there was an ABS issue - apparently the wheel shaft has coding gears to count the rotations and one of the "teeth" was in a bad way. He changed the whole shaft.

    This issue does not bother me too much but I'd rather not give up the use of the engine break.

    Any debugging suggestions welcome :)
     
    #1 Louis Horvath, Sep 6, 2024 at 8:58 PM
  2. Tombukt2

    Tombukt2 Senior Member

    Joined:
    Nov 29, 2020
    9,772
    1,706
    0
    Location:
    Durham NC
    Vehicle:
    2009 Prius
    Model:
    Base
    When my '09 was doing almost exactly this my hybrid battery was actually going south at the time I didn't know it but quickly got up to speed. And that's the only thing I can think of that would have been making that happen and there were other things going on too but that's not for this discussion. As soon as the hybrid battery was replaced a whole bunch of problems went away but I do remember this region breaking business kind of just not working at a pretty slow speed 10 miles an hour or something along those lines and like it just clicked off I don't think it does that now I'll check it in the morning I rarely use my friction brakes until I'm at the stop sign and I have to clamp on the rotors to not roll forward or backwards that's about the only time I'm clamping with the hydraulics where I'm driving I have nothing but time.
     
    #2 Tombukt2, Sep 6, 2024 at 9:15 PM
  3. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    109,445
    49,754
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    idk much about engine braking, but isn't 6-12mph the area where regen cuts out and full friction braking takes place?
     
    #3 bisco, Sep 6, 2024 at 9:52 PM
  4. TMR-JWAP

    TMR-JWAP Senior Member

    Joined:
    Aug 12, 2016
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    Location:
    Columbia, SC
    Vehicle:
    2007 Prius
    Model:
    Touring
    I have to ask....why do you use the B function so much?
     
    #4 TMR-JWAP, Sep 6, 2024 at 10:13 PM
    Tombukt2 likes this.
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