Strange engine behaviour -- like revving while stopped at light

Discussion in 'Gen 3 Prius Main Forum' started by TheHorsts, Mar 28, 2018.

  1. TheHorsts

    TheHorsts Junior Member

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    We have a 2010 Prius with 190,000 miles. No real problems to date. Although it is starting to burn oil (about 1 qt every 2500 miles) and our MPG seems to be declining (this may be related to the below).

    However, lately we've been noticing several strange internal combustion engine (ICE) behaviours:

    At stop lights and will essentially full battery, the engine will slowly ramp up to ~2000 RPMs and then back down before turning off. All of this is about a 45 seconds long. We most commonly notice this at the end of a freeway off ramp where we are coasting to the stop at the light.

    Additionally, it seems to frequently immediately kick on the engine when starting from a stop even with a very light touch in ECO mode.

    And one last symptom. When accelerating out of our driveway, it sometimes feels like the car stalls out for 1/2 second before the ICE engine kicks on.

    Its been to the dealer and they found nothing. All they did is look at various computer codes, but found nothing. They suggested that our hybrid battery may be getting to the end of life, but offered nothing to back that up.

    Any suggestions about what is happening would be hugely appreciated!
     
  2. bisco

    bisco cookie crumbler

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    they could be right, but it is not so far out of balance to throw a code yet.

    have you checked the 12v health? how old is it?
     
  3. Mendel Leisk

    Mendel Leisk Book Cover Judge

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    I've noticed odd rev up directly after a 12 volt battery disconnect, during warm up, say within the first minute or two of start up. And this is for just the first one or two startups. I get the sense mine was some sorta recalibration.

    In your case, might be similar process, with different trigger?
     
  4. Raytheeagle

    Raytheeagle Senior Member

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    Have you ever changed the transmission fluid?

    Are there any periods during acceleration at highway speeds that you notice hesitation?

    Do you ever have issues with cold start knock at the beginning of the day?

    Ever clean or check the hybrid fan?
     
  5. Jayw13702

    Jayw13702 Active Member

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    My 2010, 2005 and 2004 Prius’s have all done the same thing when they get a bit of mileage on them (150,000 plus)
    On the 2010 I have changed the trans oil, inverter coolant, cleaned the egr cooler and none of this has stopped this behaviour, I have now concluded that it’s something that happens on higher mileage cars with full batteries


    2010 Gen 3
     
  6. rau

    rau Junior Member

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    Had the same high rev when stopped. Sent in for hybrid battery change.
     
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  7. Erik Owens

    Erik Owens Member

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    This almost sounds like and EGR issue but you would probably be experiencing misfires and possible DTC.
     
  8. TheHorsts

    TheHorsts Junior Member

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    Did the hybrid battery change fix the behaviour?
     
  9. TheHorsts

    TheHorsts Junior Member

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    Thanks for the suggestions.

    This Prius has been religiously maintained (fluid changes, etc.), the 12v battery has been replaced, there's no blockages to the hybrid battery fan, etc.

    Usually, when the engine is revving at a stop sign, the battery is full or very nearly full.

    It's all very strange.
     
  10. bisco

    bisco cookie crumbler

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    when the battery is full the engine may rev to burn off excess electrons.
     
  11. Jayw13702

    Jayw13702 Active Member

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    I have read this somewhere else as well


    2010 Gen 3
     
  12. FuelMiser

    FuelMiser Senior Member

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    The computer is revving the ICE to "burn off" excess battery charge. The electrics are spinning the gas motor, but no gas is being burned. It is simply protecting the HV battery from over-charging...happened all the time in our Gen 2. An older NiMH Traction Battery loses efficiency as it ages, i.e., can't store as much energy, discharges sooner and charges faster than when new. The car still regenerates as much energy as always since it still weighs the same, but the battery cannot store as much as before. Thus, the computer has to "burn off" this excess energy.
     
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  13. Mendel Leisk

    Mendel Leisk Book Cover Judge

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    Sign of failing battery then? :(
     
  14. FuelMiser

    FuelMiser Senior Member

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    More like a degraded battery. It is still functioning, just not as efficiently as when new. You may notice lower MPG, but you are still able to drive normally. Failing batteries are indicated by transient warning lights (triangles/exclamation points) and messages (Hybrid System Failure), and inability to enter Ready mode.
     
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  15. GFO

    GFO Member

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    ^ I read that as "Car Has Too MUCH Power!" and that put a smile on my face.
     
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  16. Grit

    Grit Senior Member

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    I agree with Mendel and FuelMiser. Driving on SF hills, had 8 bars (75% SOC on techstream) for 5 straight minutes and still driving downhill then came to full traffic stop. Engine has yet rev'd up.
     
  17. Mendel Leisk

    Mendel Leisk Book Cover Judge

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    They can do a hybrid health check with techstream I think? If you google that with Toyota at the beginning you'll find some info.
     
  18. TheHorsts

    TheHorsts Junior Member

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    This doesn't quite seem like our case.

    We're completely stopped before as the revving takes off. I.E. there's nothing that that would generating any additional electricity at that point. Not sure were an excess battery charge would be coming from. All braking (regenerative or otherwise) has stopped since the car is stopped.
     
  19. padroo

    padroo Senior Member

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    Have you ever cleaned the MAF air flow sensor and I bet your throttle body is really dirty. A dirty throttle body will cause a high idle, cheap to clean. It may have never been cleaned.
     
  20. BZzap!

    BZzap! Senior Member

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    I’m thinking the same thing. The throttle plate may be slightly cracked open due to sludge and carbon build-up. If that’s the case, the throttle position sensor can send erroneous date back to the ECM and cause a high idle. As “padroo” suggests, it might be time to thourghly clean the TB.