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Autopilot slowing down for no apparent reason

Discussion in 'Model S' started by Phoenixhawk101, Jun 22, 2016.

  1. Phoenixhawk101

    Joined:
    Feb 28, 2015
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    Location:
    Chicago, IL
    So driving home today I was on a 55mph stretch of road that I take each way to work each day. Even though it is a 55 zone most people travel at about 75 or 80 (yea yea yea). In the past autopilot has had no issues at 75 on this road but today (@ about 6pm so still bright and sunny, completely empty road and straight) the car just suddenly slowed down to 65. No error message about "5 over" came up (and the car was doing more than 5 over).

    Has anyone run into anything like this? I found a similar video on YouTube::


    This was obviously night and may have been that he camera could not see far enough, but mine happened in the daytime...

    Thoughts?
     
  2. kort677

    kort677 Active Member

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    Location:
    florida.
    it saw a ghost? in all seriousness unless this becomes a regular occurrence I wouldn't get all worked up over it. it is still a beta
     
    • Like x 1
  3. Phoenixhawk101

    Joined:
    Feb 28, 2015
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    Location:
    Chicago, IL
    Not too concerns outside of the mustang behind me had to slam on the brakes to not hit me (he was tailing too closely as it was). More than anything was just curious if anyone had seen similar. Since it happened I have now been able to recreate the issue two additional times this evening. I'll try to get video the next time.
     
  4. Tdriver

    Tdriver Member

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    Check your tire pressures. When one of mine dropped to 39 psi the cruise would not go over 65.
     
    • Like x 2
  5. chillaban

    chillaban Member

    Joined:
    May 5, 2016
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    Location:
    San Jose, CA
    So I know this is not your situation, but I actually had a pleasant experience with Autopilot slowing my car down today on my commute. A car in front of me in the neighboring lane swerved a few inches into my lane boundary as I was approaching at a 20mph speed differential. My Tesla suddenly slowed for that and did not pass the offending car until I hit the gas myself. Not sure if that was coincidence or a feature, but in any case, it was well executed.

    I'm guessing in some of your cases, maybe some safety system like TCS/ESP had to make small interventions due to road imperfections and that triggered a slowdown. It'd be helpful to see a video, because the linked video slowed down at quite a gradual pace.... That's my typical "I think I'm going into a speed trap" slowdown rate, and I sure hope nobody tailgates me to the point that it's an issue :D
     
  6. dohmer

    dohmer Member

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    May 19, 2016
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    Location:
    Burnaby, BC
    I had a similar experience the other day. Driving at 100kmh with no cars anywhere close to me. I felt a jolt as regenerative brake engaged to slow down for no reason. Took me a second to react and I just stepped on the go pedal and away I went again. If I didn't step on the go pedal, I think it might have stopped the car. I thought the radar got confused but no indication on the console. Haven't seen it again.
     
  7. kort677

    kort677 Active Member

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    did you ignore the AP Nags? ignoring them will cause the car to gradually slow or this might be some sort of software bug associated with that feature
     
  8. SherSlick

    SherSlick Member

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    Jan 30, 2015
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    Location:
    Denver, CO
    Mine has done this as well. I think it sees what it thinks is a speed limit sign that is under the 45 cutoff and starts coming down rapidly.

    That OR it decides its no longer a multi-lane road and this triggers the massive slowdown.
     
  9. Ciaopec

    Ciaopec Member

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    You have obviously been around long enough to glance at the speed limit picture. I have trouble on Ohio roads, particularly OH 25. Cruising at 65 and the car reads the OH 25 sign and starts slowing me. Not so bad on OH 65. Don't know what other state road signs look like as I haven't traveled that many "by-ways-out-of-state". Doubt that is your problem here; just a thought . It does get my attention when it slows rapidly; so far nobody too close behind.
     
  10. kort677

    kort677 Active Member

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    that could be, my AP sometimes does not limit me on some roads when it should and on one road in particular which is a 3 lane highway it does limit the speed when AP is on
     
  11. mspohr

    mspohr Active Member

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    I've noticed AP slows on some curves. I assume it does some kind of calculation of the "safe" speed to take a curve.
    We have a very winding section of I-80 and it will slow on some of the sharper curves.
     
  12. grichard

    grichard Member De-Luxe

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    I have trouble with it mis-reading signs sometimes, too.

    On my commute home, it sometimes interprets "weight limit 55 tons" as a 55mph limit.
     
  13. S4WRXTTCS

    S4WRXTTCS Active Member

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    From the OP's description we have no idea what component of AP caused the slowdown.

    The TACC component is not in Beta, and it's just as likely to cause the car to slowdown as AP.

    I primarily use TACC and occasionally I get a few sudden slow downs with no perceptible cause. I expect TACC to occasionally get confused in corners when there is a car in front of me, but in the other lane. Oddly it seems to handle that case pretty well. Not perfect, but not like the old adaptive cruise control systems of old.
     
  14. OLD BOATER

    OLD BOATER Member

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    Location:
    Rancho Cucamonga, CA 91730
    Mine is near flawless. As example, today from Newport Beach CA to Rancho Cucamonga, a 2 hour drive in heavy stop and go. It never misses perfection unless the white line is too far from the two yellow lines (maybe in CA). I use cruise control even in town to prevent running into the guy who cuts me off...
     

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