car jumped forward while slowing down near complete stop

[momojuice]

I was driving on a boulevard at the speed limit of 70km/h, the traffic lights ahead turns red. I let go of accelerator and start to press brake pedal with force slightly above usual as the light was close for my speed. The car slows down in a constant manner toward the light 70..60..50..40..

However just as it come near to complete stop (at about 10-20 km/h). This odd behavior happened: the car suddenly jumped forward for a fraction of second before continue to slow down to complete stop. It almost felt like a burst of acceleration was applied or at least to say, it felt like the brake pedal was released momentarily, then reapplied. But my right foot was on the braking pedal applying constant force during this whole time. My wife at passenger seat also felt the jumpy motion so I'm not hallucinating.

The road was clear, no snow/rain. So it's not tire slippage. But it is winter and the regen was very limited, almost none.

I've noticed this happened a few times already, it's not a one-time event. Has anyone experienced the same?

 

[GtiMart]

There's just about no way the friction brakes would have reduced by themselves. What I have felt sometimes was the car feeling some slipping of at least one wheel and momentarily reducing regen when that happens. That feels like if the car accelerated, and there is obviously less stopping power, but that doesn't mean friction brakes were reduced. Your total stopping power is regen + brakes and if regen reduces, if feels like brakes reducing, or the car accelerating (relatively speaking).

 

[KenC]

That's likely the "blended" brakes, where the regen braking switches over to friction braking. That strange feeling where the car may feel to have accelerated, isn't actually acceleration, it's less deceleration.

I used to get that in my Chevy Volt, since that vehicle has always had blended brakes. People always would write on message boards that the car accelerated.

Turn off your blended brake toggle, and see if you still get that feeling from time to time.

 

[Audiotronics]

I have noticed while driving with autopilot engaged you can come to a complete stop due to the car in front of you as intended(or also slow down a bit) . but if that car in from turns and makes an opening the car will think it needs to accelerate back up to speed even if it’s a red light

 

[Lindenwood]

I have noticed while driving with autopilot engaged you can come to a complete stop due to the car in front of you as intended(or also slow down a bit) . but if that car in from turns and makes an opening the car will think it needs to accelerate back up to speed even if it’s a red light

Autopilot does not and is not intended to stop at red lights. It is only supposed to stay between the lines at the pre-set speed and not hit things in front of you. Sounds like it functioned as designed.

 

[Audiotronics]

Autopilot does not and is not intended to stop at red lights. It is only supposed to stay between the lines at the pre-set speed and not hit things in front of you. Sounds like it functioned as designed.

Yes I know this this that what’s I was explaining to the OP

 

[Lindenwood]

Yes I know this this that what’s I was explaining to the OP

Ah, I see! I am not sure this would apply with the brake pedal depressed, though.

 

[Audiotronics]

Ah, I see! I am not sure this would apply with the brake pedal depressed, though.

only during one pedal driving. Which is kinda dangerous if you ask me. With so much power in a tesla, if someone bumped you from behind and your foot is over the l pedal this car could rocket forward.

 

[Lindenwood]

only during one pedal driving. Which is kinda dangerous if you ask me. With so much power in a tesla, if someone bumped you from behind and your foot is over the l pedal this car could rocket forward.

More explicitly: The Autopilot is disabled once the brake pedal is depressed, which the OP describes was the case. Therefore, there is no way the autopilot would have caused the experience the OP describes.

 

[Audiotronics]

More explicitly: The Autopilot is disabled once the brake pedal is depressed, which the OP describes was the case. Therefore, there is no way the autopilot would have caused the experience the OP describes.

maybe it’s the anti lock brakes kicking in on black ice? Since the op says it’s cold

 

[Lindenwood]

maybe it’s the anti lock brakes kicking in on black ice? Since the op says it’s cold

Very possible, if it was icy, that the vehicle momentarily reduced regen if it sensed a wheel(s) sliding!

 

[MountainPass]

Very possible, if it was icy, that the vehicle momentarily reduced regen if it sensed a wheel(s) sliding!

This is my guess!

 

[kimwin]

Autopilot does not and is not intended to stop at red lights

I found that with autopilot (TACC) , my car automatically slows down and stop when it sees red light ahead, note that my car was the only car at this red light. It even start moving when the light turns green, quite amazing. Tested this behavior so many times and I am convinced it does. However, I am always ready to take over control if it does not stop for some weird reason.