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ICE keeps turning on during commute

Discussion in 'Gen 2 Prius Fuel Economy' started by philaprius, Nov 8, 2007.

  1. philaprius

    philaprius New Member

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    I have been driving my 2007 Prius for several months now. It's performed as expected for the most part (my commute is 3-4 miles in the city) and I seem to get 36-38 mpg on average on those trips, 50 mpg on the highway on my weekend trips, and closer to 55-60 mpg when I get to drive in the burbs.

    My question is this. Sometimes the ICE turns on again in the middle of my drive. It does an ignition cycle on start up as usual and then turns off after 5 minutes (after which I can pulse and glide). However, five to ten minutes later after the engine turns off at a stoplight, it will suddenly turn on again and stay on until I come to the next complete stop. Then it functions normally again, kicking in only when I accelerate. If I stop again, the engine sometimes comes on again until the next stop. It's weird. I don't use the AC or heat when this is happening and my battery is 3-4 bars, so I can't think of another reason the ICE would be turning on.

    This doesn't happen every day.. maybe just once a week. Any ideas/insight as to why this would happen? Any thoughts are appreciated...
     
    #1 philaprius, Nov 8, 2007
  2. efusco

    efusco Moderator Emeritus
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    Probably the cold weather...such a short commute you're probably not getting the ICE temp all the way up.

    Consider grill blocking and an engine block heater...it'll help that short commute mileage a lot, give you a warm cabin sooner, and stop that unnecessary wasteful ICE starting.
     
    #2 efusco, Nov 8, 2007
  3. douglas001001

    douglas001001 smug doug

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    It sounds like you might be getting the passing 80 deg c water pump cycle, where the ice won't shut off if it turns on in the middle of it. Usually lasts like a minute.. some force shutoff with ev switch when this occurs.

    Since you are saying you can p&g after 5 minutes, you've at least crossed the 70 deg c barrier and this happens a few minutes after that, so that is my guess.
     
    #3 douglas001001, Nov 8, 2007
  4. philaprius

    philaprius New Member

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    <div class='quotetop'>QUOTE(efusco @ Nov 8 2007, 04:03 PM) [snapback]536874[/snapback]</div>

    Thanks for the input. Sadly, I don't have a garage so an engine block heater is not possible.... Also, it's happened during the summer as well so I'm not sure if it's due to the ICE not getting warm enough. It happens after the initial ignition cycle for the ICE (at which time I assume it has reached its internal temp). The ICE then turns off so I can pulse and glide. Then for some reason it turns on again at a stop light and stays on until I come to the next complete stop, at which time it starts behaving normally, allowing me to P+G again...

    <div class='quotetop'>QUOTE(douglas001001 @ Nov 8 2007, 04:16 PM) [snapback]536881[/snapback]</div>

    Thank you too for your input. This explanation sounds interesting but I don't quite understand.. What is the 80 deg C water pump cycle? Is this normal behavior for my Prius? It really drops my mileage, and will stay on for minutes until I come to a stop, which seems to put things back in order with the ICE staying off. Although as I mentioned, it might happen again a few minutes later at another stop sign.

    I can't go into a EV only mode while the ICE is on it seems. The only way I've stoped it is to halt the car completely which isn't always feasible...

    Thanks again!
     
    #4 philaprius, Nov 8, 2007
  5. philaprius

    philaprius New Member

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    <div class='quotetop'>QUOTE(douglas001001 @ Nov 8 2007, 04:16 PM) [snapback]536881[/snapback]</div>

    Thank you too for your input. This explanation sounds interesting but I don't quite understand.. What is the 80 deg C water pump cycle? Is this normal behavior for my Prius? It really drops my mileage, and will stay on for minutes until I come to a stop, which seems to put things back in order with the ICE staying off. Although as I mentioned, it might happen again a few minutes later at another stop sign.

    I can't go into a EV only mode while the ICE is on it seems. The only way I've stoped it is to halt the car completely which isn't always feasible...

    Thanks again!
     
    #5 philaprius, Nov 8, 2007
  6. douglas001001

    douglas001001 smug doug

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    <div class='quotetop'>QUOTE(philaprius @ Nov 8 2007, 05:51 PM) [snapback]536896[/snapback]</div>
    When the coolant temp passes 80 degC, the water pumps come on, I think it is to mix the coolant that is stored in the thermos. Someone else would have to give more on the specifics, but the ice probably stays on so the battery doesn't get used for this process.

    Last winter I didn't have a scan gauge to monitor this, I don't remember if it happens every time you cross over the threshold, but if you are P&g'ing and your coolant temp is around 80 and the weather is colder you can bounce above and below that every few minutes. Its down in the 40s here now, I'll report back as I'll probably encounter this more frequently in the next few days.

    As efusco suggests, try grill blocking as this will help to keep the heat in once you're up to temp (use search function on here for many threads).
     
    #6 douglas001001, Nov 8, 2007
  7. efusco

    efusco Moderator Emeritus
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    You're probably not in Stage 4 and what you're experiencing at the first stop is that you're slowing from a speed higher than 35mph and the car will go into stealth from that speed.
    At the second stop I'd venture that you are slowing to a stop from a speed below 35mph...since you're not in S4 the ICE will continue to run for about 5-6 seconds at that stop. Once it shuts off while stopped you're in stage 4 and it should shut off at any speed when you slow down.
     
    #7 efusco, Nov 8, 2007
  8. morpheusx

    morpheusx Professor Chaos

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    If its cold outside as much as you may want the cabin heat try turning the heater fan to the lowest speed or off and try a lower temp. Test it out at a stop light or drive thru and most likely your ICE will instantly turn off. The higher the settings the more heat it is drawing from the coolant, therefore forcing the ICE to warm the coolant back up.
     
    #8 morpheusx, Nov 9, 2007
  9. JimN

    JimN Let the games begin!

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    Philaprius, the ICE is running to either keep itself or you warm. If you turn off the climate control or reduce fan speed at the traffic light and the engine turns off then it is a question of your personal comfort. (Don't get the cabin too cold as the battery needs some heat which is obtained through the vent by the back seat. Low 70's should be OK. It really depends on how much sun the car gets.) Placing pipe insulation in the grill retains heat so the ICE doesn't have to run as much to keep itself warm.

    There is a tow truck driver in the neighborhood that runs an extension cord from the house to the truck parked on the street.
     
    #9 JimN, Nov 10, 2007
  10. wyounger

    wyounger New Member

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    With such short commutes the car may need to run the ICE extra here and there so it can squeeze in all of the self-tests of the emissions system required on 1996-up vehicles. There is some background business getting done and with these very short drive cycles it might just need extra ICE time for the test routines to finish.

    Even if it's the case I'm sure it's still frustrating. Just keep in mind that Toyota doesn't have 100% flexibility to be green; they have to conform to the same regulations as everyone else too.
     
    #10 wyounger, Nov 29, 2007
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