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Engine revs on freeway after letting go of gas

Discussion in 'Gen 2 Prius Main Forum' started by Brando714, Jul 28, 2020.

  1. Brando714

    Brando714 Member

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    Weird thing occurred yesterday while on the way back home on the freeway. I was driving about 80mph and when I let go of the gas, I'd here it revving but not accelerating faster. When I plugged in my bluetooth OBDII and opened up TorquePro, sure enough it confirmed that the RPM increased. Today on the way to work in the early A.M. it did not do this. Any ideas whats going on?
     
    #1 Brando714, Jul 28, 2020
  2. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    My theory is that your car was trying to discharge the battery a bit until it cooled off. It would be interesting to monitor fuel usage (predicted: zero) and cabin temp/battery fan intake temp (predicted: high) during these events.

    It seems like the computer does not want the battery to get very full unless it knows it is breathing cool cabin air during the charge. If it can't solve the cooling side of the equation, it dumps stored energy to solve the 'full' side of the equation. Spinning the engine with zero fuel is an effective energy sink.
     
    #2 Leadfoot J. McCoalroller, Jul 28, 2020
    Isaac Zachary likes this.
  3. AzusaPrius

    AzusaPrius Senior Member

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    Were you going down hill when you noticed this, if so you may be due for a transmission fluid change.
     
    #3 AzusaPrius, Jul 28, 2020
  4. bisco

    bisco cookie crumbler

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    likely a weak hybrid battery, or throttle body problems.

    how many miles on your car?
     
    #4 bisco, Jul 28, 2020
  5. Brando714

    Brando714 Member

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    No, it was flat and I've done a transmission fluid change 2 months ago
     
    #5 Brando714, Aug 1, 2020
  6. Brando714

    Brando714 Member

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    175K miles and the paid Dr Prius app showed battery life as 61% and 2 months ago I cleaned the throttle body
     
    #6 Brando714, Aug 1, 2020
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  7. Brando714

    Brando714 Member

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    It just happened again this morning while going to work at 5AM so battery was cool temp. It's weird because of owning the car for 2 months, this happened recently and does it intermittently. I'm still averaging the same MPG so I guess in that sense it's not really burning up much more fuel than normal
     
    #7 Brando714, Aug 1, 2020
  8. bisco

    bisco cookie crumbler

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    might be a good time for a prolong reconditioner
     
    #8 bisco, Aug 1, 2020
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  9. Isaac Zachary

    Isaac Zachary Senior Member

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    I don't know if it would be worth it, but maybe if you could confirm the state of charge through the Torque app when it happens? If the battery is deemed full it would do that. Or anytime the car decides not to charge the battery. It seems that I've had it happen in my Avalon when the battery was probably hot (mountainous driving).
     
    #9 Isaac Zachary, Aug 1, 2020
  10. Brando714

    Brando714 Member

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    While I had it on the display where it shows the battery bar, it was normal (about 2/3 of the bar)
     
    #10 Brando714, Aug 1, 2020
  11. donbright

    donbright Active Member

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    were you by any chance in cruise control ?

    i ask because i seem to remember having weird problems w acceleration when i was in cruise, possibly related to my cruise button being intermittent non-working, but im not 100% sure of my memory
     
    #11 donbright, Aug 5, 2020
    Last edited: Aug 5, 2020
  12. Isaac Zachary

    Isaac Zachary Senior Member

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    This happened to me the other day... And then I realized I was in "B" mode... (Actually "4th" in the Avalon.)
     
    #12 Isaac Zachary, Aug 5, 2020
  13. robinredd1

    robinredd1 Junior Member

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    My engine does that revving up after releasing my foot off the gas pedal too and when it does that for me it's because the 12 volt battery is low needs to be charged I have a short or a wire in the car that drains my 12 volt battery slowly and when the car starts doing that revving thing I know the battery is low and needs to be charged so 12 volt battery because all kind of weird things to go on loose connection on the battery terminals weird things to go on so I hope this helps anybody
     
    #13 robinredd1, Jun 8, 2024
    Last edited by a moderator: Jun 8, 2024
  14. dbstoo

    dbstoo Senior Member

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    No one touched on the fact that the CVT provides a mechanical link between the motor and the wheels that synchronizes the speed that the motor spins with the speed of the wheels. It can only run the wheels at a certain speed without spinning the motor.

    80 MPH is way over the speed that would allow freewheeling.
     
    #14 dbstoo, Jun 8, 2024
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