1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Strange behavior with engine not cutting out

Discussion in 'Gen 4 Prius Main Forum' started by Steve Ball, Dec 8, 2022.

  1. Steve Ball

    Steve Ball Junior Member

    Joined:
    Jan 4, 2016
    17
    8
    7
    Location:
    New York
    Vehicle:
    2021 Prius
    Model:
    LE AWD-e
    All -

    My 2021 Prius has exhibited a strange behavior a few times - strange, but not necessarily bad. Just I think it is a little quirky.

    On my commute (mostly highway, 65-70mph, about 45minutes driving), if I let off the gas pedal, the car rolls along - and downhill, will pick up speed pretty swiftly. Engine seems completely off, even if >64mph (and EV) in this.

    However last night: it seemed like the engine was not cutting off, and was remaining on, even if a little bit - car did not roll as much downhill (pick up speed as much) as engine was definitely on a little bit. Hmmm. I put the car into 'B' and this was noticeably different - engine braking (and engine noise) much more apparent - but back to 'D' and engine definitely was not cutting out as normal. Even if engine was somehow on, MPG meter was all the way to top (100MPG+) so whether engine was on but very lightly fueled, I don't know.

    Car stayed this way pretty much the whole ride back, very, very hesitant to switch to EV at <64mph, even on downhills. Battery was at mixed ranges - 2 bars from empty and all the way to 2 bars from full - and car did this across all of these.

    Didn't do it today.

    Wonder if there is something specific? No warning light, car is fine, MPG is fine - just the engine was still being ran for some reason.

    ??
     
    #1 Steve Ball, Dec 8, 2022
  2. CooCooCaChoo

    CooCooCaChoo Senior Member

    Joined:
    Jan 7, 2015
    930
    522
    0
    Location:
    Cow-lee-fornia
    Vehicle:
    2023 Prius
    Model:
    LE
    Most likely the cold. Even though you can ride along in EV mode, the engine still needs to be a certain temperature in order to operate optimally. You being in New York is gonna make the engine run for longer periods to stay in the correct temperature range.
     
    #2 CooCooCaChoo, Dec 8, 2022
    Pulse07 likes this.
  3. Steve Ball

    Steve Ball Junior Member

    Joined:
    Jan 4, 2016
    17
    8
    7
    Location:
    New York
    Vehicle:
    2021 Prius
    Model:
    LE AWD-e
    I don't think it's the cold. It will cut out just fine in the cold once warmed up - and yesterday was around 50F so not too cold. Something was directing the car to keep the engine on. To add, the graphic showed battery and wheels (no power feed from engine) even though I could hear and feel the engine was on slightly.
     
    #3 Steve Ball, Dec 8, 2022
  4. Doug McC

    Doug McC Senior Member

    Joined:
    Feb 15, 2022
    1,014
    382
    0
    Location:
    Midwest
    Vehicle:
    2022 Prius
    Model:
    XLE
    The display isn’t always reality. The system is monitoring a multitude of parameters and starts and stops the ICE for as many reasons. Air temperature, hybrid battery temperature, use of electrical devices (fan, lighting, heaters), having the cabin heater on, even the radio, etc. can result in the ICE running to meet anticipated electrical and other energy requirements, among many other factors. Trust the system to protect itself. The display is telling you (primarily) the “driving” and “regenitive” force.
     
    #4 Doug McC, Dec 8, 2022
  5. CR94

    CR94 Senior Member

    Joined:
    Dec 2, 2014
    2,642
    1,140
    0
    Location:
    Northwestern S.C.
    Vehicle:
    2011 Prius
    Model:
    Two
    How are you determining whether the engine is "on" in those circumstances? Above a certain speed (about 45 mph for 3rd generation, maybe higher for 4th) the engine always continues to rotate slowly while you're coasting, although fuel delivery is shut off if the engine is warmed up and happy. Whether it is rotating at borderline road speeds isn't obvious, unless you have added instrumentation that can show (for example) engine speed.
     
    #5 CR94, Dec 8, 2022
  6. Steve Ball

    Steve Ball Junior Member

    Joined:
    Jan 4, 2016
    17
    8
    7
    Location:
    New York
    Vehicle:
    2021 Prius
    Model:
    LE AWD-e
    I could feel it (more resistance while going down hill, less tendency to speed up) and hear it a little too. Again, not as severe as 'B' (which I tested), and today's commute it did not happen at all: when coasting down hill, engine force was not noticeable nor audible, which is why - since I'm so used to it - the car's behavior the other day was strange.

    Anyway - other poster stated perhaps other things going on. As I said, this is an intermittent and has happened maybe a handful of times over the past year - so I was just wondering if this was (is) a known thing that happens.

    Yes, agreed on all - the car of course looks after itself - so was just wondering more than anything.
     
    #6 Steve Ball, Dec 9, 2022
  7. Doug McC

    Doug McC Senior Member

    Joined:
    Feb 15, 2022
    1,014
    382
    0
    Location:
    Midwest
    Vehicle:
    2022 Prius
    Model:
    XLE
    The short answer to your question is “yes, it is a known thing.” These are fascinating vehicles, and the more we learn about them, the more fascinating they become.
     
    #7 Doug McC, Dec 9, 2022
  8. robsnyder20

    robsnyder20 Active Member

    Joined:
    Aug 13, 2012
    374
    301
    0
    Location:
    SW Florida USA
    Vehicle:
    2016 Prius
    Model:
    Three
    I would say this is somewhat typical especially at this speed. Mine (2016) never likes cutting back to 0 rpm running in the 60's (but it can up to 72 MPH and does sometimes). If running the cruise control its much less likely to cut out the engine then if your driving with the pedals also. I have a scan gauge so I can tell pretty easily if my engine is truly running or not.
     
    #8 robsnyder20, Dec 10, 2022
  9. BiomedO1

    BiomedO1 Senior Member

    Joined:
    Mar 27, 2021
    1,835
    930
    0
    Location:
    SacTown, Ca
    Vehicle:
    2021 Prius Prime
    Model:
    LE
    LoL; Here's a joke: How do you tell if a guy is a Prius owner or a Motor-head?

    Answer:
    A Prius owner asks, Why doesn't my motor cut off or shut-down.
    A Motor-head asks how do I fix my motor cutting-off - Dude; you need to bypass your speed sensor.
     
    #9 BiomedO1, Dec 10, 2022
(You must log in or sign up to post here.)