Strange behavior and cold weather

Discussion in 'Gen 2 Prius Main Forum' started by TomB985, Feb 10, 2019.

  1. TomB985

    TomB985 Member

    Joined:
    Apr 20, 2014
    137
    64
    0
    Location:
    Isanti, MN
    Vehicle:
    2006 Prius
    Model:
    Two
    Good morning, everyone.

    I'm fortunate enough to have an insulated garage that stays substantially warmer in the winter than it does outside. The majority of this winter my car has started in the morning at 30 to 40°F rather than the significantly colder temperatures we've had outside.

    Yesterday it got its first run in a week-and-a-half after sitting outside, it was 5° out. It started and drove just fine, but I noticed some interesting engine behavior when I got on the highway. Beyond a certain throttle point the engine would rapidly change rpm from midrange to near redline and back again. Power output seemed to remain constant, and I never had any check engine lights, so I'm wondering if this is part of the cold-weather warming strategy? Has anybody else experienced anything similar?

    It acted like this a few weeks ago after being parked overnight and starting at -15°, but normal operation resumed when the engine got up to temperature. This thing takes a LONG time to warm up when he gets this cold.
     
  2. JC91006

    JC91006 Senior Member

    Joined:
    Nov 10, 2013
    13,739
    6,360
    0
    Location:
    Los Angeles, CA
    Vehicle:
    2010 Prius
    Model:
    V
    If it's normal after it warms up, I wouldn't worry about it.

    Good time to check your fluid levels though (coolant/oil)
     
    Raytheeagle likes this.
  3. oil_burner

    oil_burner Active Member

    Joined:
    Feb 26, 2017
    223
    104
    0
    Location:
    Canada
    Vehicle:
    2006 Prius
    hard to say, but it is a very good idea to check all fluids. Also consider a grill block, it is around -10F here the last couple weeks, I have both top and bottom grilles completely blocked with cardboard. No overheating even on the highway for 45 minutes my water temperature only gets up to 185.
     
  4. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    80,824
    34,790
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    check the 12v health. could be the hybrid battery is showing its age
     
  5. George W

    George W Active Member

    Joined:
    Mar 12, 2018
    302
    139
    0
    Location:
    San Antonio
    Vehicle:
    2008 Prius
    Model:
    Touring
    we had a cold snap this past week, just before a fuel stop. When the gas pump clicked off , not as much capacity, im gueszing the bladder contracted somewhat. It distorted the indicated .mpg, 4 miles greater than actual (calculated by the odometer track). It was the first time I've seen a skewed indication coinciding with a temperature change.
     
  6. TomB985

    TomB985 Member

    Joined:
    Apr 20, 2014
    137
    64
    0
    Location:
    Isanti, MN
    Vehicle:
    2006 Prius
    Model:
    Two
    Thanks, guys.

    The 12 V battery was new three months ago, and has given me no indications of an issue. After sitting for 10 days it had no issues starting the system, and likewise my hybrid battery was showing nearly full bars after that time. I check coolant and oil regularly, all of which have been changed in the last few months and are showing right within range. It's probably nothing to worry about, I just figured I would ask.

    Have you noticed as much of a difference with this? I've always been skeptical, in theory with a closed thermostat there should not be any coolant flowing to the radiator, so I've never attempted to block anything off.

    I haven't noticed any skew in MPG, but I have a harder time getting a full reading on the fuel tank, and it seems to be holding less fuel. I figure it's normal for the temperature and age of the car, but definitely a strange quirk with the previous compared to other cars.
     
  7. oil_burner

    oil_burner Active Member

    Joined:
    Feb 26, 2017
    223
    104
    0
    Location:
    Canada
    Vehicle:
    2006 Prius
    I've noticed a huge benefit, big decrease in warmup times and fuel economy for short trips much improved. I keep an eye on the invertor temperatures with the torque app on my phone though. I think with the thermostat as soon as it heats up the heater core and starts to open up to the radiator it gets a rush of freezing cold coolant, then keeps having to heat that loop slowly.
     
    TomB985 likes this.
  8. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    12,355
    5,940
    90
    Location:
    Western Washington
    Vehicle:
    2012 Prius
    Model:
    Three
    The heat loss isn't just from the radiator, but also from the engine block and everything else behind the radiator.

    Massive wind chill, though not being bare human skin, the common wind chill charts are not correctly scaled for it. A grill block reduces that too.
     
    TomB985 likes this.
  9. Skibob

    Skibob Senior Member

    Joined:
    Sep 14, 2018
    2,376
    1,165
    0
    Location:
    Northern California
    Vehicle:
    2006 Prius
    Model:
    N/A
    So when it’s that cold out how long do you guys let your cars warm up before you drive? Do you like start the car then go back inside and have a coffee or breakfast or something?
     
  10. TomB985

    TomB985 Member

    Joined:
    Apr 20, 2014
    137
    64
    0
    Location:
    Isanti, MN
    Vehicle:
    2006 Prius
    Model:
    Two
    This always makes a thread really long, because everybody has their own opinion. Lol much like an oil thread.

    I start mine and drive immediately, making sure to be easy on the throttle until the engine comes up to temperature. Just like every other car. Everything I’ve read suggests that running below operating temperature is not good for an engine, and idling is the most inefficient way for an engine to warm up. So I try to get mine up the temp as fast as possible, even when it’s cold out.
     
  11. Skibob

    Skibob Senior Member

    Joined:
    Sep 14, 2018
    2,376
    1,165
    0
    Location:
    Northern California
    Vehicle:
    2006 Prius
    Model:
    N/A
    I think there is a point where it’s better to let the car run a few minutes to warm up. If for no other reason than to let the oil warm up enough to not open the bypass valve so much. What is that temperature? I don’t know but 5 degrees would be in that window.
     
  12. TomB985

    TomB985 Member

    Joined:
    Apr 20, 2014
    137
    64
    0
    Location:
    Isanti, MN
    Vehicle:
    2006 Prius
    Model:
    Two
    I've not read that, but not saying it's false either. If you can find a source I'm all ears, I'm always up for challenging my assumptions.

    I did a lot of reading about this over the years, as is always a topic that comes up on Internet forums and such. I'm kind of obsessive about efficiency is well, so I start off being biased against letting an engine run for no reason. I get comp at any data or reputable source that suggests that is necessary. The only exception were the two diesel pickups I had in the past, both had a note in the owners manual about the PCM forcing idle-only for as much is 20 seconds during "extremely cold weather". I don't believe I ever saw this message come up, and my understanding was that it had more to do with the fuel system than anything else.
     
  13. Skibob

    Skibob Senior Member

    Joined:
    Sep 14, 2018
    2,376
    1,165
    0
    Location:
    Northern California
    Vehicle:
    2006 Prius
    Model:
    N/A
    I have no documentation that letting the car idle a few minutes might be a good idea. Just seems 5 minutes of letting the car warm up can’t hurt. I say do what you want. Your the one having the problem, not me.
     
  14. TomB985

    TomB985 Member

    Joined:
    Apr 20, 2014
    137
    64
    0
    Location:
    Isanti, MN
    Vehicle:
    2006 Prius
    Model:
    Two
    Haha...now that turned quick. You were asking about how long people let their cars idle, and now it's "You're the one having the problem, not me". Nice.

    My engine is working just fine, thanks.
     
  15. Skibob

    Skibob Senior Member

    Joined:
    Sep 14, 2018
    2,376
    1,165
    0
    Location:
    Northern California
    Vehicle:
    2006 Prius
    Model:
    N/A
    Glad to hear it.
     
  16. oil_burner

    oil_burner Active Member

    Joined:
    Feb 26, 2017
    223
    104
    0
    Location:
    Canada
    Vehicle:
    2006 Prius
    I have a lot of short drives, my daily commute is now about 3 miles. My timer on my block heater is set for 3 hours beforehand. Then I let my car idle for about 10-15 minutes, less than 10 minutes I don't get heat. So the last 3 weeks have been around -5 to -12F. My average MPG is anywhere from 25-34. It does not get better if I skip the idling.

    I have observed that the car will simply not get to temperature if I am doing stop and go and driving in town, 35-40mph speeds. Only after about 45 minutes to an hour will the car reach operating temps. That is with complete grill block with cardboard/tape. That is not based on coolant alone but also MG1 and MG2 temperatures. When the oil and MG1/MG2 are not warm, there is a lot of drag in the drivetrain. I have to use a lot more throttle than normal.

    Now today I had to sit in the car and idle for about 2 hours. Coolant, oil, and transmission temps were all hot by the time I was able to drive. I reset my trip counter and my 11 mile commute was back to 47mpg, the car felt so much better, very little rolling resistance and I was able to pulse/glide normally. I am getting ready to do an engine swap, but while I am poking around I'm going to see if I can install some additional form of heating element to warm the transmission. The block heater simply doesn't cut it. Ideally I would have 3x heating elements bringing the coolant, engine oil, and transmission oil all up to temperature. Then I bet I could hit 40mpg on my 3 mile commute.
     
  17. TomB985

    TomB985 Member

    Joined:
    Apr 20, 2014
    137
    64
    0
    Location:
    Isanti, MN
    Vehicle:
    2006 Prius
    Model:
    Two
    I'm a bit south of you in Minnesota, but we've had a relatively cold winter for the most part. In contrast, most of my driving is highway miles, and I roll over 2000 per month with my typical schedule. My car was not built with a block heater, and I never have one installed, but it has the advantage of starting from an insulated garage that's always a good 30° warmer than outside temps.

    In the worst of the "polar vortex", overnight temps went down to -30°F and my garage was around 10°. But even during those subzero temperatures my fuel economy never dipped below 35 miles per gallon. My worst tank was the most recent one I filled had the most idling to clear the windshield off. The fact that I can get above 35 mpg with no idling at all suggests to me that cold transaxle and sub-optimal engine temperatures are less harmful to fuel economy than extended idling.

    I haven't driven it much in the last two weeks because my van is in the shop for a warranty repair, and their150 mile-per-day allowance means I put most of my miles on the brand-new Jeep Cherokee they put me in. I hope to get my van back in the next couple of days, and my Prius will stop feeling so neglected.

    [​IMG]
     
  18. oil_burner

    oil_burner Active Member

    Joined:
    Feb 26, 2017
    223
    104
    0
    Location:
    Canada
    Vehicle:
    2006 Prius
    an insulated garage definately helps. My car is parked outside so if the coolant temperatures aren't at least about 140F before I set off, there is not enough heat to keep the windshield from fogging and freezing on the inside. Then I have to pull over after 5 minutes to scrape the inside of the windshield.
     
Loading...