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ICE didn't shut off when fully warmed -- what happened?

Discussion in 'Gen 3 Prius Technical Discussion' started by fuzzy1, Mar 17, 2010.

  1. fuzzy1

    fuzzy1 Senior Member

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    Can anyone figure out what happened here, or provide more ideas what I should look for next time?

    Monday I had a repeat of an earlier anomaly in which the ICE continued operating in conditions where it should halt: stop lights and sub-40 glides long after warm-up is complete. And daily MPG (I reset TripA each morning) was unusually low.

    While it may have happened several times, two cases really stand out. The first was (I hope) coincidentally the first commute after installing Adrian's first new GenIII ScanGauge codes. At 9 miles into the commute, with fully warmed coolant, the engine kept idling at stops, and the day's MPG was at 43 in a location where normal is mid- to high-50s. A shutdown and restart at the next light cured the problem.

    Monday it happened again. A different route meant it wasn't noticed until 12-15 miles into the trip. More ScanGauge codes went in ten days ago, so I was monitoring MG1 RPM and Torque. At stops, engine sound was present, MG1 was spinning, torque was zero. Moving at 30-35 mph, MG1 RPM was in the 100-500 range, again with zero torque. This must mean the ICE was idling under gasoline power, but producing no traction or electric generation. SOC 6 bars, no defrost, very little cabin heat. At 15 miles, with MPG again running abnormally low, a shutdown and restart cured the problem. MPG then climbed for the short remainder of the trip.

    Tuesday's ride was normal. At stops, MG1 RPM was zero. On the 30-35 mph stretch, with ICE halted, MG1 RPM was 3500-4000. Outside temperature was low- to mid-40s F each day.

    Any idea what was happening here? And could similar anomalies contribute to the low MPG that some readers have complained about?
     
    #1 fuzzy1, Mar 17, 2010
  2. Prius 07

    Prius 07 Member

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    Since you have a Scangauge can you please provide more data:
    The actual FWT temp and do you see it dropping? This is something that also happens with me and there can be many contributing factors.
    Even after reaching the desired coolant temp you can lose heat and fall below the level where ICE will run. You can lose heat if you're running the heater - as an experiment when you're stopped watch how quickly your temps drop as shown on your Scangauge. I find once I reach 175 / 180 and been there for a while then I can maintain the desired temps, but often 164 can quickly decline below the temps that will make the ICE come on. Of course outside temps are a factor too and you indicated in your post that it is cold enough to be a significant factor.
    FYI my ICE also comes on at times when I don't believe it should above 164 even 175 and 180 (more rare at the higher ends) and I usually can force it off by varying pressure on the gas pedal; applying the brakes to varying degree or by stopping completely. Can't exactly explain it but it happens to me also.
    Best of luck,
     
    #2 Prius 07, Mar 17, 2010
  3. Prius 07

    Prius 07 Member

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    deleted - duplicate post
     
    #3 Prius 07, Mar 17, 2010
  4. bestmapman

    bestmapman 04, 07 ,08, 09, 10, 16, 21 Prime

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    When this happens to me, I turn off the heat. That always immediately shuts the engine down. Where was your heat temperature set at.
     
    #4 bestmapman, Mar 17, 2010
  5. Prius 07

    Prius 07 Member

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    bestmapman - thanks and I have the same experience in that situation. What I was suggesting to the OP is to monitor the FWT on the Scangauge as even after reaching the desired temp if running the heater/defrost it can lower the coolant temps so the ICE remains / comes on. I personally hardly ever use heat and mostly use it when I have to defrost and use it on very low settings 64 -66F. If my car has been warmed up for a while I can actually run the defrost on those low settings with the ICE remaining off when stopped. My personal situation described in my original reply was to illustrate to the OP that the ICE being on unexpectedly is not unique to him. My example was when I try to glide and ICE stays on with fully warm coolant temps.
     
    #5 Prius 07, Mar 17, 2010
  6. efusco

    efusco Moderator Emeritus
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    When it's cold out running the heat, at all, can keep the ICE running. As suggested, turn the heat off and it should allow the ICE to shut off and the car to get into S4 assuming your ICE temp stays up.
     
    #6 efusco, Mar 17, 2010
  7. bwilson4web

    bwilson4web BMW i3 and Model 3

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    I too found the heater can leave the ICE running at a stop. I'll turn off the heat, the engine stops, and when the light changes, accelerate and start the heat again.

    Bob Wilson
     
    #7 bwilson4web, Mar 17, 2010
  8. fuzzy1

    fuzzy1 Senior Member

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    Heat was 66F, with fan low, on the second bar. This has been my standard setting most of the winter.

    I didn't have fWT up this time, but will bring it up next time. In the event noted two months ago, it was about 190F.

    When this happens, it seems to go on for multiple stops and hills and glides. I don't really pay attention to single Auto-Stop failures.
     
    #8 fuzzy1, Mar 17, 2010
  9. Prius 07

    Prius 07 Member

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    WOW @ 190F it should definitely go off. Occasionally I've hard time getting in stealth mode at as high as 183F.

    If you have your heat on and you can shut it off then try shutting it off and when the ICE goes off then try to turn it on again. Other than that you seem to be doing everything right.
     
    #9 Prius 07, Mar 17, 2010
  10. David Beale

    David Beale Senior Member

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    There's a caveat here too. I've seen the coolant temp drop -below- the ICE on temp (64C for Pearl) yet the ICE doesn't start. All the way down to about 50C. But the car has to be driven for quite a while before this happens and has to have been fully warmed up.
    Note also that traction battery charge level can force the ICE to run to charge it.

    Just face the facts. The Prius is smarter than most of us and we may never understand it at all times. ;)
     
    #10 David Beale, Mar 17, 2010
  11. Rokeby

    Rokeby Member

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    The ICE-ON condition could be to (re)heat the catalytic converter.

    I suppose this would be most likely if the grills were fully blocked
    keeping the ICE warm, but air moving under the car cooled the cat'.

    IIRC, the Gen III has a bunch of other piping under the chassis for
    ICE heating on start-up that might also have some effect here.
     
    #11 Rokeby, Mar 17, 2010
  12. fuzzy1

    fuzzy1 Senior Member

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    My lower grill is blocked. I'll add Adrian's (generic) cat temperature gauges, and check those and fWT next time. But after extended idling and a couple hill climbs, it seems odd that the cat could have cooled that much.

    I've experienced the ICE firing up from falling coolant temperature and SOC numerous times during stop-and-crawl traffic, but those events don't run on like these two did.
     
    #12 fuzzy1, Mar 18, 2010
  13. hobbit

    hobbit Senior Member

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    The way I try to be smarter than my Prius in this regard is to
    kill the fan when I go into a long glide or a stop, and only
    try to let it draw heat from the engine when it's *running*
    for the most part. Actual temp set to maybe 66 or 67, just
    above the "max cold", and whether or not heat is actually produced
    is all dependent on fan run or not. A little bit of heat
    drifts into the cabin anyways if the set temp is above max cold,
    and often that's plenty to keep me comfy on a given trip by
    itself. Unless I need more serious defogging.
    .
    _H*
     
    #13 hobbit, Mar 18, 2010
  14. randyj

    randyj New Member

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    In my limited experience (with my Gen-III) when I occassionally find the ICE running when I don't expect it to, the dashboard battery indicator is showing "low". It makes sense that the ICE will need to run when the electric motor is low on juice -- because I've already been using electric power a whole bunch around town. (I seldom have the heat on). I understand that this dash-graphic of the battery does not really represent 0 to 100% but is only "some upper" percentage (?) of the actual battery charge, but it still may be relevant to your issue.
    -rj
     
    #14 randyj, Mar 18, 2010
  15. fuzzy1

    fuzzy1 Senior Member

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    Two things point away from the battery charge:

    (1) SOC (battery State Of Charge) was 6 bars, its preferred 'home';

    (2) MG1 torque was zero, meaning no electric generation could be taking place at MG1.

    Excluding bugs, it seems that the only other reason for the ICE to run is heat. I'll watch that much closer next time.

    Tonight's commute contained more stop-and-crawl than normal, running down both coolant temperature and SOC, but did not recreate anything similar to the incidents mentioned in my OP.
     
    #15 fuzzy1, Mar 18, 2010
  16. F512M

    F512M Member

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    +1, I had the same thing happen and when I shut the heat the engine shuts down.
     
    #16 F512M, Mar 18, 2010
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