Stuck Throttle?

[zarwin]

The feeling was that of getting thrown back in the car, like when you're accelerating, [...]

I do not doubt you at all, and while the following is somewhat unrelated, something to keep in mind.

I was driving my '10 Prius and had the braking issue while approaching a turn. The road was torn up and ABS engaged as I initially started to brake and suddenly I felt the car accelerate. Though I would swear up and down that it accelerated, what actually happened is the re-gen turned off when the ABS engaged and I was not pressing very hard on the brake so the brakes were not actually engaged. ABS switched on but did not slow the car at all until I pressed harder on the brake.

Now why would I think it accelerated and then later know for sure that it did not? Well I went back and did it over and over on that same corner trying to figure out what actually happened, and it did occur every time. The second time it still felt a little like an acceleration, the third and subsequent it just felt like a coast.

The first time I was thrown back into the seat as if the car was accelerating, but that was due to me automatically (sub-consciously?) pushing against the steering wheel in anticipation of slowing down. When something completely unexpected happened my brain processed it as something it wasn't. I still vividly remember the feeling the first time of the acceleration that was not there. Kinda like that trick where you push down on someones arms and they swear they float up when you let go.

-Zarwin

 

[LEAFer]

Zarwin "jogged" my memory of an incident ...

Have you ever picked up a (for example) can of soda, which you expected to be full or nearly full (heavy) ... but it wasn't ? :shock: What a weird feeling as the can shoots up off the kitchen counter. (Turns out my wife had emptied it in the few minutes I had left the kitchen. :lol: )

 

[aqn]

If it is repeatable, please give the exact required steps
so that we can try it (and perhaps variations) on our LEAFs.
Thanks.

I'll take careful note on my commute tonight, but I'm pretty sure a steady and constant "somewhat serious" deceleration coming to a complete stop in ECO will reproduce this behavior (with less than 100% SoC). (If the rate of deceleration scale has "I see a red light and I'm coasting up to it" at one end (zero) and "I didn't see the red light and now I'm slamming on the brakes" at the other (ten), I'd say "somewhat serious" deceleration is about a three or four.)

I think it happens within the last five feet prior to the complete stop. It feels about the same as if you suddenly lift off the brakes a [i[tiny[/i] bit and re-apply it within a fraction of a second.

I checked it out again. You'd need more like a 5 or 6/10 in braking effort, and it happens in the last two feet prior to the complete stop.

 

[garygid]

If I can remember, ... what? :lol:
I will try ECO "heavy" braking (but with steady brake pressure) to a full stop.

 

[gbarry42]

Been there, done that, got the T-shirt. I got to live through the whole Prius thing two years ago, complete with road tests and showing the better half how you can put it in neutral, or force the power off, and...how stepping on the brake instantly releases the throttle. I haven't tried that last one on the LEAF, but I gotta think it will. Then, that's all you'd need to know.

I also went through the "I'm concerned, because I know how firmware works" process, in the process discovering that the pedal has two independent sensors, that the engine computer is separate from the controls computer and will stop (or go really slow) if it loses communication with it (or gets funny messages). This doesn't eliminate the possibility entirely, but makes the chance extremely rare. Such that we could drive LEAFs for 10 months now without a single report of this on MNL. I'd say unless there's a direct cause, the OP won't ever see this again.

I also went through everyone asking me if I was afraid to drive the Pruis (just like they all asked me how I got home in the LEAF when all the power was off ). The T-shirt (I wasn't kidding) has the Toyota logo, and says, "Once you drive one, you'll never stop".

You all can try an experiment...you may be able to get this particular feeling. With the car in motion, put you braking foot on the floor and press as if you were pressing on the brake pedal. You may get this feeling as though the car were on ice. This even works for me when I'm a passenger. If you can feel it, you can get an idea of the sensation. That will help you discriminate between "no brakes" and "lurching forward".

I have experienced the switchover from regen to friction brakes, and the "ABS-slip-on-a-bump" event, but I heard about all of these before ever experiencing them. They're fairly subtle, and knowing about them ahead of time just takes away the surprise factor.

 

[RT3]

I will update with more information later, but my wife just reported the same problem with our LEAF. I just finished speaking with my local Nissan dealer. The LEAF will be getting towed over to the dealer for diagnostic checks. Scary doesn't even begin to describe the problem, but I really like our LEAF. Hopefully, Nissan will get to the bottom of this quickly.

 

[TomT]

All Nissans since 2006 have brake override (which shuts down the throttle if the brake is also pressed), so this is most puzzling...

 

[mwalsh]

Yes, had something similar happen twice. But I remember it being a cruise control issue rather than a braking issue (I had this rather bad habit of using the cruise control and ECO level regen to slow the car rather than the brakes). I'll pay better attention to the circumstances, should it happen again:

http://www.mynissanleaf.com/viewtopic.php?f=8&t=6086&p=270190#p270190" onclick="window.open(this.href);return false;

 

[lincomatic]

Sorry, I thought I updated this thread with my conclusions a while back, but it looks like I didn't.
After owning the car for several more months, I started getting this sporadic problem where the brakes sometimes get
super grabby. Even when the car is barely moving, no matter how lightly you press the pedal, they will just clamp down forcefully,
throwing you into your seat... the brakes basically feel like they're binary.

Another random phenomenon is sometimes the car feels like an ICE engine that's stuck in fast idle ...
let off the brake pedal, and the car lurches forwards at a much faster rate than normal, as if you're slightly depressing the accelerator pedal.
When both of these phenomena occur simultaneously, it feels a bit like the way my wife described.

She now concurs with my analysis, that there was no stuck throttle situation, and has grown accustomed to the strange random behavior.
It's annoying, but not dangerous. I've been wondering when Nissan is going to figure out how to fix this, and update our cars.

 

[davewill]

Sorry, I thought I updated this thread with my conclusions a while back, but it looks like I didn't.
After owning the car for several more months, I started getting this sporadic problem where the brakes sometimes get
super grabby. Even when the car is barely moving, no matter how lightly you press the pedal, they will just clamp down forcefully,
throwing you into your seat... the brakes basically feel like they're binary. ...

Well known problem, search for "grabby brakes". Yes, there's a fix available.

 

[kubel]

Well known problem, search for "grabby brakes". Yes, there's a fix available.

There is? I had the brake update done. It didn't completely fix the problem, just made it a little more bearable.

 

[lincomatic]

Sorry, I thought I updated this thread with my conclusions a while back, but it looks like I didn't.
After owning the car for several more months, I started getting this sporadic problem where the brakes sometimes get
super grabby. Even when the car is barely moving, no matter how lightly you press the pedal, they will just clamp down forcefully,
throwing you into your seat... the brakes basically feel like they're binary. ...

Well known problem, search for "grabby brakes". Yes, there's a fix available.

Thanks. I'll get it done next time I take the car in for the battery check. Any fix for the "high idle?"