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Autopilot on Freeway slowed down to a crawl twice today!

Discussion in 'Model S: Driving Dynamics' started by jlucero, Jun 4, 2016.

  1. jlucero

    jlucero Member

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    here was the situation...we were on an empty freeway the other day and it was raining and windy...the route was 50 miles, and autopilot worked fine the majority of the way. then all of a sudden, autopilot went from 65 mph to 30 mph and stayed there...was pretty alarming. the speed limit didnt change, as i was on a freeway. we kept going and turned AP back on, and it happened again a minute or so later. i suspect something must have blocked one of the sensors, but didnt seem that likely as the whole trip was raining. on the second time, i didnt do anything and wanted to observe if the speed would crawl back up (freeway was pretty empty), but it stayed around 30-35mph, and then eventually cars caught up and i had to drive faster. AP worked fine the rest of the trip....any ideas as to what is going on?
     
  2. svp6

    svp6 Member

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    I do not think it is a sensor issue. When the radar is blocked, cruise control cannot be engaged at all.
     
  3. Az_Rael

    Az_Rael Active Member

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    I am pretty sure rainy conditions are spelled out as a limitation in the manual for TACC and Autosteer. I am guessing the water was causing sensor ghosts or something
     
  4. Bladerunner

    Bladerunner Member

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    Did it wrongly pick up a road sign for a speed limit (from actual road or from an overpass, parallel road, etc.)?
     
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  5. TaoJones

    TaoJones Beyond Driven

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    TACC has been doing that more in the last month on the freeway. Dry conditions, wet conditions, doesn't seem to matter.

    Didn't lose AP features in a torrential sustained road-flooding downpour on the interstate this past week. That was nice.

    But TACC has been slowing for ghosts for no apparent reason more lately - no idea why. I'd like to think it's because it's sensing more and not misaligned.
     
  6. kort677

    kort677 Active Member

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    there is a simple remedy for when the TACC slows when you don't want it to, engage right foot, add downwards pressure to the accelerator pedal and maintain your desired speed. in all seriousness are your sensors being blocked by dirt? the only time my car will slow on it's own is when in AP and the nags are ignored. I would guess a trip to your service center is in your future.
     
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  7. jlucero

    jlucero Member

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    you bring up a good point...cause both times it slowed down to 35 mph or so...but cant imagine what it picked up. like i said, it was raining pretty much the whole ride, so hard to believe that extra rain blocked all the sensors. car is not muddy by the way, pretty clean.
     
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  8. TaoJones

    TaoJones Beyond Driven

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    Yeah, that's called a workaround - not a
    (re)solution. In SoCal, we don't let our sensors get dirty :).

    Further, I'd rather not clog an SvC with a problem they aren't likely to fix. A better approach is to call the ownership support line, have them pull the logs, and request that the behavior/bug is reported to engineering/dev. While the logs will probably go to an SvC for review anyway, at least it doesn't take up an appointment slot and possibly a loaner, which just makes things worse.

    Tesla would do well to capture a top-10 of these use cases in which visits to an SvC could be avoided with a correctly-directed phone call. In the specific example above, if the logs indicate sensor misalignment, then sure, make an appointment. But if there's nothing in the logs and the sensors are clean in dry clear weather, then it's a bug. Probably a "working as designed but not as intended" bug. Those are special. But I digress.
     
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  9. Tree95

    Tree95 Member

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    The OP said he was on an empty freeway. The AP speed limit of 5MPH over last seen speed limit sign doesn't usually occur on freeways. AP treats freeways and non-freeways differently, but I'm sure it doesn't always get the distinction correctly (especially when a road transitions between a divided freeway and non-divided highway).
     
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  10. kort677

    kort677 Active Member

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    the slowing thing happened to me yesterday, it was on an fairly empty 3 lane highway, speed limit of 65 mph. I had the tacc set at 72 mph and was on ap. no cars adjacent and one car was a 2k+ feet ahead of me going slow. all of a sudden the car starts to slow down, I was down to 60mph and was about 1k feet behind that car in front. I moved over a lane and the car resumed it's set speed. My conclusion is that the TACC sensed the slower car at a great distance and began to slow down. This is unusual behavior and I didn't think that the TACC's "visibility" was that far down the road. nonetheless there was no panic, I just took steps to alter the car's actions.
     
  11. Tree95

    Tree95 Member

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    Yeah, this pisses me off. On lightly traveled freeways in the west, if I'm doing 70 and there is a truck doing 55 ahead, TACC will suddenly do a full regen brake when I'm still a football field or more behind the truck. Very annoying for me and passengers.
     
  12. GKwey

    GKwey Member

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    It would happen on I-90 from Mariina Del Ray onramp to almost the I-405 transition, because I think the autopilot still follow the 40 miles speed limit (for the local side street in parallel). It also would happen in downtown on I-110 where there are several overpasses above with the lower local street speed limit. Software fixes are needed.
     
  13. brucet999

    brucet999 Active Member

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    Do you mean that the car sees speed limit signs an the frontage road or that NAV knows speed limits of adjacent roads but gets confused about what road it is actually on?

    I recently had AP limit my speed when I engaged it with 70mph ACC speed set while leaving a small town on US 395. It apparently read "End 35 mph zone" as "35 mph zone".
     
  14. dhanson865

    dhanson865 Active Member

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    NAV knows speed limits of adjacent roads but gets confused about what road it is actually on

    It's been discussed by a number of people. One in particular in Canada rails about this because in his case they widened the roads into a highway but the NAV still thinks its a back road so he can't use autopilot at full speed on that highway.
     
  15. Joeski1

    Joeski1 Member

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    oops!! The system in't purrrrfect!! Not yet..... anyway..... very annoying... yes.. I drive manually 98.9% of the time....

    Call me nuthin' more tan a "pig headed" human.. but i feel I still drive better than a Tesla with either the AP or adaptive cruise control or both ganging up on me!!
     
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  16. NDR

    NDR Member

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    All three of our teslas (2-p85d 1-x90d) started recently slowing down while in AP at the exact same spot on the sawgrass expressway southbound by the bbt stadium where the old toll booth was... They only do this when they are navigating to my house. Maybe it has something to do with predictive off ramp behavior due to destination? The problem is my exit isn't for another 5 miles.
     
  17. Tdriver

    Tdriver Member

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    Could one form of AP slowing be tied to the speed of the wipers?
     
  18. pdxgibby

    pdxgibby Member

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    #18 pdxgibby, Jul 7, 2016
    Last edited: Jul 7, 2016
    I had this happen to me on my commute to work twice this morning. No rain. Cloudy skies. 56 degrees F.

    Heading South on I-5 between Elligsen Rd. and Wilsonville Rd. in Wilsonville, Oregon. Cruise was set at 72 mph. Speed limit was 65mph. The speed limit shown on the dash was 65mph. Autopilot engaged, very light traffic.

    On both occassions, I was cruising along with my hands on the wheel using autopilot. The car just started slowing. It was not aggressive (as in emergency braking), but appeared to be full regen, as in the acceleration was completely overridden.

    The first time it happened, I was just about even with the Elligsen Rd. exit. The car started slowing and I looked for clues as to why. No ghost image on the dash, nearest car was quite a ways ahead of me. I interrupted autopilot and cruise control and kept driving, as there was some traffic coming up behind me.

    The second time it happened, I was in the right hand lane almost exactly between the Elligsen Rd and Wilsonville Rd. exits. Cruise control and autopilot engaged. Speed limit shown in IC showed 65mph. Cruise was set to 72mph. There wasn't much traffic behind me, so I let it keep slowing to see what would happen. I eventually took over at ~42mph as I didn't want to be unsafe as traffic was approaching.

    I contacted the Tesla Support phone number and explained the issue. They opened a case and my local service center would follow up from here.

    All sensors / radar / camera were clean.
     
  19. Boatguy

    Boatguy Member

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    I was driving on a frontage road and the MS picked up the freeway speed limit! So I'm sure it can error in the opposite direction as well.

    Or the rain / muck off the road fouled the sensors.
     
  20. pdxgibby

    pdxgibby Member

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    Update on this issue:

    On the way home from work yesterday, I had a similar experience going the opposite direction in a similar area of the freeway. Cruise control set to 72mph. Cloudy skies. Autopilot on. Speed limit on instrument cluster showed 65mph.

    All of a sudden, the car slowed to 42 mph. It was not holding the speed by providing a small amount of power, instead it was giving a good amount of power to accelerate, then it would go to full regen, and then accelerate, then regen. It cycled like this for about a mile until I interrupted it. I tried to get a recording of this behavior, but unfortunately, my cellphone battery died 9 seconds into my video. :(

    This morning on my drive into work, I tried to reproduce it again, but I didn't have any problems. Will keep an eye on this one and see if I can record video of it happening again.
     

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