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Engine turning on at low speed/acceleration

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Pandalover, Aug 31, 2012.

  1. Pandalover

    Pandalover Junior Member

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    I have noticed that recently my engine seems to be coming on when I accelerate from a stand still even with very slow acceleration.

    For example today: battery over 50%, foot off break and onto gas very gentally, 0 to 10 in about 4 seconds at about 8 mph I feel the engine kick in.

    Over the last few days it has seemed like the engine has been running a lot in town or when moving slowly in heavy traffic.

    If I press the ev button I can accelerate quiete aggressively before the engine will start.

    Economy seems a little down from usual 55mpg to 52mpg but may not be related.

    Any ideas what's going on? :(
     
    #1 Pandalover, Aug 31, 2012
  2. Dorian7

    Dorian7 Junior Member

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    Are you using the HSI screen? If you let that bar crossover the halfway line it will run the engine. Also is the car fully warmed up when this is happening?
     
    #2 Dorian7, Aug 31, 2012
  3. Pandalover

    Pandalover Junior Member

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    If the HSI screen is the one with picture of the car on then yes. I can also feel/hear the engine come on at that speed.

    I noticed the problem again this afternoon at the end of my 20 mile commute so I would say it would have been warm.
     
    #3 Pandalover, Aug 31, 2012
  4. Dorian7

    Dorian7 Junior Member

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    Sorry, I didn't realize this was Gen II. If there are no check engine lights on then the only thing I can think of is that you are just pressing a little to fast/hard with the pedal. I know mine can be very touchy. How many miles are on your car?
     
    #4 Dorian7, Aug 31, 2012
  5. Pandalover

    Pandalover Junior Member

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    Its very gental, just enough force to get the pedel to move and for the car to move faster then just rolling in drive.

    Only 23k miles on the clock and dealer serviced so far.
     
    #5 Pandalover, Aug 31, 2012
  6. Dorian7

    Dorian7 Junior Member

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    Hmm, well the only other idea that I can think of is maybe your battery is getting too low and doesn't have enough power so the engine is kicking in -- This happens to me sometimes when I am doing extended EV trips.
     
    #6 Dorian7, Aug 31, 2012
  7. uart

    uart Senior Member

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    Hi Panda lover. How are you measuring the "50%" state of charge. How many bars are showing on the graphic for the state of charge.
     
    #7 uart, Aug 31, 2012
  8. Pandalover

    Pandalover Junior Member

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    I measure battery charge by the centre console display - 5 or more bars - it's over the little half way nub according to the centre console.

    The engine starting with very very gently acceleration seems to happen no matter how many bars I have but Im particularly surprised to hear the engine come on when the battery appears over half full.
     
    #8 Pandalover, Sep 1, 2012
  9. uart

    uart Senior Member

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    Ok good. I wasn't sure if you were just using the graphic or measuring the exact value via pri-dash or something.

    The two main things that I've noticed make it reluctant to use the battery are:
    1. State of charge (SOC), and
    2. Battery temperature.

    I notice that mine is really eager to run in EV mode if it's on 7 (green) bars. It's also pretty good on 6 (top blue) bars. At 5 bars it still holds EV mode ok, but I'm starting to have to be a little more gentle on the accelerator. From there it seems to pretty much be a sliding scale with every bar less making it more and more difficult to make it deliver EV-only power. At 3 bars it will pretty much kick off the engine at the slightest power demand, and under 3 bars I'd say that EV mode is all but non-existent. This is all normal (as designed) operation as far as I can tell.

    The other thing I've noticed is that battery temperature also plays a role. I don't have any direct way to measure batt-temp but I have noticed that when the fan is running faster in the rear vent that it also becomes more reluctant to use EV mode. The first summer that I had the Prius (bought s/h) I noticed the fan in the back sometimes running pretty fast and EV mode becoming very reluctant. I ended up cleaning out the battery cooling fan and finding it was significantly blocked up with dog hair and gunk.

    Next time you have a medium-long trip on a hot day (especially one with lots of hills), leave it in ready when you stop and then go place your ear next to the vent at the back seat and listen to how fast the fan is running. If it's running faster than just a whisper then your battery may be getting a bit warm. Take a look at my photos (reply #31) in the following link to see how to check and clean the fan. See: Fur and dirt causing major battery problems | Page 2 | PriusChat
     
    #9 uart, Sep 1, 2012
  10. Pandalover

    Pandalover Junior Member

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    It dose not get too hot here but I will check it out. I do have a rather heary dog so it's a possibility that the fan is clogged.
     
    #10 Pandalover, Sep 1, 2012
  11. uart

    uart Senior Member

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    Yeah big hairy dogs a major cause (check my avatar to see how I know that). So check it out. :)
     
    #11 uart, Sep 1, 2012
  12. PriusRoadWarrior

    PriusRoadWarrior retired

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    Do you have your AC on?
     
    #12 PriusRoadWarrior, Sep 1, 2012
  13. Pandalover

    Pandalover Junior Member

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    uart I gave it a go but could not figure out how to get the main bit of trim off with out taking the whole car apart so admitted defeat.

    PriusRoadWarrior same problem with a/c on or off.
     
    #13 Pandalover, Sep 1, 2012
  14. uart

    uart Senior Member

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    Yeah I know what you mean. I nearly admitted defeat the first time I tried to get it apart too. But it turns out that there's only a few screw fasteners (from memory I think about three) and the rest of it just "pops" apart. Get a wide bladed screw driver or even a butter-knife and just feel for the attachment points and pry them off (except for the actual screw fasteners of course).

    I know it feels awful disassembling stuff like this where you just have to pry it, I always feel like I'm going to bust something, but it does come apart reasonably easily once you get the hang of it.
     
    #14 uart, Sep 1, 2012
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