I leased a BMW i3 for a couple years before I purchased my S and every time I went over a bump while slowing down, it would lose regenerative braking and it did indeed feel like it was accelerating. I had to be careful in certain spots. If anyone in the NJ area is familiar with the eastbound Harrison exit on I-280, you go down a hill and right before the traffic light there's a bunch of bumps and the i3 lost it there every time. The S doesn't do it a that spot, but there may be circumstances in which it does.
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Another Sudden Acceleration
- Thread starter Omnomynous
- Start date
PWlakewood
Active Member
100% agree. Happens to me daily at the same spot at a stop light on my way home.
Worth pointing out these two posts by @wk057:
Sudden Unexpected Acceleration today
Sudden Unexpected Acceleration today
TL;DR - it was pedal misapplication that caused your car to unintentionally accelerate.
Sudden Unexpected Acceleration today
Sudden Unexpected Acceleration today
TL;DR - it was pedal misapplication that caused your car to unintentionally accelerate.
LN1_Casey
Draco dormiens nunquam titillandus
If you think this is reoccurring problem, a nice, reliable way to completely exclude--to your own belief--the possibility of accidental petal application is to set up a cheapo dash cam at your feet, able to see your foot as it's applied to the pedals. Then you'd also have evidence to present to Tesla techs.
You should be able to identify the moments of 'acceleration' by your aforementioned screaming. ;-)
You should be able to identify the moments of 'acceleration' by your aforementioned screaming. ;-)
@Electric Dream , definitely the regen is cutting off, but there is more going on than that. It disables itself every winter when it's cold enough and you get that weird feeling as you let off the accelerator that the car is sliding. I know that sensation well. But in this case it's not just coasting, it's accelerating. It literally scared me. The road was clear and dry and there was no reason for the car to compensate for any traction issue, it's just baffling.
And I have a blackvue, so I went to check the video, but the stupid thing stopped recording back on 5/22, card is failing. So I ordered a new 128 sd card and am gonna put the rearview cam in the foot well tonight.
@Enginerd , you are exactly right. I messaged Tesla to ask them to check the logs right after I made my appointment, hope they get to them in time. Need that data.
And I have a blackvue, so I went to check the video, but the stupid thing stopped recording back on 5/22, card is failing. So I ordered a new 128 sd card and am gonna put the rearview cam in the foot well tonight.
@Enginerd , you are exactly right. I messaged Tesla to ask them to check the logs right after I made my appointment, hope they get to them in time. Need that data.
If you run the camera, try and get the car's speed and power meter in view. I really don't think it is accelerating i.e. applying power by itself. It may feel that way, but you need some objective way to measure what's actually going on.
An app on your phone might help. I don't think a lot of those are particularly accurate for this sort of measurement, but maybe worth a try.
An app on your phone might help. I don't think a lot of those are particularly accurate for this sort of measurement, but maybe worth a try.
@commasign The universe would make so much more sense if I could just remember it that way. Every time I hear about these incidents I always think the people involved are the same ones who think Alexa is sentient. As a person who laughs at those people it's very confusing to have suddenly joined them.
The car stopped, so I definitely hit the right pedal. I didn't switch pedals, but the car definitely accelerated. The car accelerated with my foot on the brake, but the car definitely can't do that.
The car stopped, so I definitely hit the right pedal. I didn't switch pedals, but the car definitely accelerated. The car accelerated with my foot on the brake, but the car definitely can't do that.
@Electric Dream the blackvue, once it's recording again, will cover that. It shows the speed. I'll have the front view cam on the windshield and the backview over the pedals (somehow). Then I just have to wait for it.
arcus
Active Member
I've noticed this behavior on a road surface with sudden drop in elevation (where two slabs of concrete vary by more than 1-2 inches from one another). It feels like the car temporarily releases brakes (hence "acceleration").
+1 on temporary loss of regen that creates the sensation of acceleration. It’s almost impossible for your body to tell the difference. Extreme example is going skydiving. Especially the first couple of times, when the chute opens, it feels like you’re being yanked UP in the sky. It is of course just a very rapid deceleration.
I agree with the previous posters. I have a consistent off-ramp that does this every time. There is a bump in the pavement (not quite speed bump sized but obvious) and if I am coasting with regenerative braking set high or lightly feathering the brakes, the deceleration is interrupted for some reason when I hit the bump.
It’s not slick when this happens. I do not use creep mode. It feels the same as when regenerative braking is turned off or the charge level is max and it’s disabled.
No idea why a road bump would cause this, but it’s a consistent quirk I’ve gotten used to. It does not accelerate, it just reduces the rate of deceleration briefly.
It did panic me a bit the first couple times because it’s close to the stop sign at the end of the off-ramp.
If anyone wants to have a go in SoCal- Southbound CA-2 exit at York blvd., just south of CA-134.
It’s not slick when this happens. I do not use creep mode. It feels the same as when regenerative braking is turned off or the charge level is max and it’s disabled.
No idea why a road bump would cause this, but it’s a consistent quirk I’ve gotten used to. It does not accelerate, it just reduces the rate of deceleration briefly.
It did panic me a bit the first couple times because it’s close to the stop sign at the end of the off-ramp.
If anyone wants to have a go in SoCal- Southbound CA-2 exit at York blvd., just south of CA-134.
Tam
Well-Known Member
I advocate barefoot driving because I can feel which pedal is which by their texture.
It might be true with old brakes without power assist but I've found no problem with power-assisted braking such as the way I pressed real hard with my barefoot below:
And when I least expected:
If you can keep an eye on the power meter in the car, you should be able to see if regenerative braking is cutting out as you describe.
Yeah, no. If it's an emergency, I don't care if it hurts my foot (which it doesn't). I routinely drive barefoot in the summer... have for years. It's safer and more comfortable than driving in flip-flops, which can easily get caught on the pedals.
Dr. J
Active Member
This sounds similar to a Toyota Prius problem: NHTSA Tracking Braking Loss on Prius Hybrids | TheDetroitBureau.com. I experienced it both in my 2006 Prius and in my ~1995 Isuzu Rodeo. Definitely not related to regen in the Rodeo; more likely an ABS issue.
Pedal misapplication is very common. The brake and accelerator pedals are pretty close together such that any slight deviation from your normal seating position (body slightly shifted, tilted, or rotated one way or another) or perhaps even the clothing you're wearing (new shoes, new socks, etc.,) could lead to a misjudgment of where your foot should go. I've seen and experienced first hand when accidentally driving using my wife's seating profile, or slightly shifted in my seat while trying to retrieve something I dropped, etc., Nothing significantly enough to cause an accident, but just a momentary disorientation where I might catch the edge of a pedal where I thought my foot was dead center on the pedal. I've seen a relative repeatedly pressing both pedals cause his feet and shoes are too big.
SucreTease
Teslarian
Disclaimer: Didn't read the whole thread, but skimmed the OP.
First, let's be clear that the car definitely did not accelerate at all here (unless the OP did hit the accelerator pedal). At worst, regen was cut to nothing and the car coasted. This caused a decrease in deceleration, but the car did not speed up on its own (unless this was downhill or something, but no power was put to the wheels is what I mean).
Without seeing the logs or anything, my guess is that this is actually a brake sensor issue, or an ABS issue... most likely the latter.
Newer Teslas (AP1+) have brake position sensors, as well as brake pressure sensors. These help the car apply an appropriate amount of regen while friction braking force increases, in order to not have a situation where the car ends up with less deceleration when you move to the brake. If these are registering more brake application than actual, the car may be commanding less regen than it should be.
A problem with the ABS can cause similar behavior if the car believes the wheels under regen lost traction. This would be evident by a TC "light" on the dash, though.
An unexpected loss of regen can and usually does feel like car is accelerating, because of the delta-acceleration registered by your butt dyno (negative acceleration to zero)... but it is in fact just no longer decelerating under regen.
Keep the power meter up. If you see this happen again, my bet is that it's a loss of regen (power meter to nothing or close to it).
Tesla should be able to confirm with the logs. If it's an ABS issue, should be a simple fix. The brake sensor side of things is harder to track down and confirm, though.
For the record, I've only personally known of this issue occurring in one Tesla vehicle... so it's not like a widespread issue or anything. Sensors go bad. It's just a car thing.
First, let's be clear that the car definitely did not accelerate at all here (unless the OP did hit the accelerator pedal). At worst, regen was cut to nothing and the car coasted. This caused a decrease in deceleration, but the car did not speed up on its own (unless this was downhill or something, but no power was put to the wheels is what I mean).
Without seeing the logs or anything, my guess is that this is actually a brake sensor issue, or an ABS issue... most likely the latter.
Newer Teslas (AP1+) have brake position sensors, as well as brake pressure sensors. These help the car apply an appropriate amount of regen while friction braking force increases, in order to not have a situation where the car ends up with less deceleration when you move to the brake. If these are registering more brake application than actual, the car may be commanding less regen than it should be.
A problem with the ABS can cause similar behavior if the car believes the wheels under regen lost traction. This would be evident by a TC "light" on the dash, though.
An unexpected loss of regen can and usually does feel like car is accelerating, because of the delta-acceleration registered by your butt dyno (negative acceleration to zero)... but it is in fact just no longer decelerating under regen.
Keep the power meter up. If you see this happen again, my bet is that it's a loss of regen (power meter to nothing or close to it).
Tesla should be able to confirm with the logs. If it's an ABS issue, should be a simple fix. The brake sensor side of things is harder to track down and confirm, though.
For the record, I've only personally known of this issue occurring in one Tesla vehicle... so it's not like a widespread issue or anything. Sensors go bad. It's just a car thing.
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