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Surging transmission when cold, why is this "normal"?

Discussion in 'Gen 2 Prius Main Forum' started by jrlittlejr, Nov 2, 2008.

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  1. Yep. The Prius is a totally different car. Ignore the surge and get on with your life.

    3 vote(s)
    42.9%
  2. Nope. Surging is abnormal. Take the car to the nearest dealer.

    2 vote(s)
    28.6%
  3. John McCain thinks the surge was a good idea. Maybe it will help the Prius too! :-)

    0 vote(s)
    0.0%
  4. Not a clue.

    2 vote(s)
    28.6%
  1. jrlittlejr

    jrlittlejr New Member

    Joined:
    Mar 19, 2005
    10
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    Location:
    Jackson, WY
    Vehicle:
    2006 Prius
    Greetings, I have a 2006 Prius 2nd generation. I've owned it since new, and prior to that had a 1st generation Prius. Recently, I moved from a temperate climate (Portland, OR) to a cold one (Jackson, WY). I've noticed when the outdoor temperature is cold (below freezing) that there is a distinct "surge" in the acceleration when I'm going from stop to highway speeds. It feels, and sounds like, the car can't decide whether to use the ICE or the electric and is switching back and forth between the two. You can hear the ICE surging, but this is not just audible, you can feel the car "surging" as it switches back and forth between the two. Some have suggested that this is caused by people "pumping" the accelerator, but I am not changing the acceleration. I can actually reproduce this with the cruise control on by setting my speed around 50, then slowing down and reengaging the cruise control. Note this is on DRY roads, so it has nothing to do with the vehicle stability system. It does improve when the engine warms up. I've read some of the other threads suggesting this is "normal" behavior and not to worry. But I would disagree this is "normal" for several reasons:

    1) It didn't occur in the same car at similar temperatures in Portland. The obvious other difference is altitude, which lends some credibility that fuel mixture in the ICE may be a factor.
    2) Not everyone who drives a Prius in cold weather reports this issue.
    3) It isn't just an auditory hallucination, you can actually feel the car "surging" which suggests that the torque to the wheels is changing.

    So... my questions are:
    1) Has anyone reporting this problem actually found a fixable problem?
    2) Does this get worse?
    3) Is this a symptom of a pending failure of the transmission/engine on the Prius?
    4) Has anyone with a ScanGuage experienced this? If so, can you contribute any data (ie what is the engine RPM doing when this happens?)
    5) Does the Prius ICE need to be adjusted for high altitude and/or cold weather operations?

    Just for fun... I'm posting a poll to get your thoughts on this issue.

    It may be time for me to get a ScanGuage and an engine block heater :)

    Thanks!
    Jim
     
  2. bwilson4web

    bwilson4web BMW i3 and Model 3

    Joined:
    Nov 25, 2005
    27,068
    15,372
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    Location:
    Huntsville AL
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
    The closest I've seen with my NHW11 is about 45 seconds after I start up, the catalytic converters will start 'working' and I can see my mass air flow jump from 7 gm/sec to 15-20 grm/sec. But I've not found a way to recreate this in cold weather.

    Last January I had occasion to drive from Huntsville to South Carolina and back in weather that started at 16F, climbed to 39F, and then back home at 18F. If was pretty much highway driving and I don't remember any 'surge' activity although I was able to follow how my MPG was proportional to the outside air temperature.

    Are you using a grill block? I'd try that first to see if has any effect on the symptom.

    GOOD LUCK!
    Bob Wilson