2011 prius strange behavior when stopping

Are you sure you are not hitting the gas pedal with your braking foot too? I believe I have done that a few times.

 

It sounds more like the ABS kicked in. You momentarily loose regenerative braking when hopping over bumps and pot holes. The jump you felt was at that point. It was a very common complaint on the 2010 Gen III's.

 

Many threads on the phenomenon here - it's not that the car surged forward, but that it stopped slowing down for a fraction of a second as you hit the bump.

This can feel like a momentary increase in speed, but isn't.

 

Several threads regarding the problem, here's one that sounds like what you experienced:

Car lurches forward while brakes are applied | PriusChat

SCH-I535

 

Your wife is not imagining things. I have a 2011 Prius Two and the same thing has happened to me several times. I have been approaching a stop sign for example and have had my foot on the brake when running over a sewer cover and the car will lunge forward. Also, when I am braking and hit a bump it will surge forward, just like the brakes are not holding. It does not happen on a daily basis but it does happen. On occasions, if a car had been stopped in front of me I would have probably rear ended it. My wife said when we went for the new car test drive with the salesman he cautioned us about that. I do not recall that as I was just thinking about the new car. I don't think there is any way that it can be controlled. If you can remember to do it which I don't seem to be able to, is maintain a little longer than normal distance behind the vehicle in front of you when you are coming to a stop in case your car lunges forward.

 

I'm a cab driver and have experienced this phenomena. It's rare. But, it sometimes does happen, but only when hitting a bump in the road whilst braking.

It's very minor. The car never losses control, but it does feel like it wants to surge. Perhaps in reality the braking is delayed by a few mili-seconds. This is real, and it doesn't matter.

 

How many miles do you have on your Prius taxi and have you had any repairs done?

 

the yellow slippery warning icon flashes when this happen, correct?

 

It's a quirk of the car. I leave additional braking space. The "surge" is when the car detects wheel slippage, disengages regen braking, and engages friction brakes. Mashing down on the brake pedal to force the engagement of friction brakes may not make it transition any faster, but it makes me feel better.

This and the non-warm-up cold start knock were the primary reasons why I recommended a Fit to my wife instead of a Prius. She's a last-second braker and she'd probably plow into someone stopped ahead of her if she hit a rough intersection.

 

This is real, and was the subject of a recall during the first model year of the Gen3 to reprogram (**shudder**) the braking logic. That firmware update reduced but did not eliminate the following loss of braking scenario: When you are gently braking (only regen braking, no friction braking) and hit a bump which causes the traction control system to realize one front wheel has lost/reduced traction, the computer holds a committee meeting during which it removes the regen braking (presumably lest you skid sideways from braking with only 1, front wheel). At the end of the committee meeting, it votes to either switch to friction braking (presumably on 4 wheels), or resume regen braking on the front wheels. During the event, you get no brakes, and stopping distance is increased. Still a problem, still rightly triggers spider senses of the driver, but scope and risk was reduced by the recall. If you hit the brakes hard, friction braking engages and you don't get this problem. Hopefully next generation will get rid of this issue...

 

I have a 2011 Prius and I experience that problem with mine as well

 

There is actually a mechanical issue as well since the regenerative braking is applied by the transaxle to the front wheels through a differential gear set. So if one front wheel losses braking torque during regenerative braking, the other one will as well. It doesn't seem dangerous (to me) except to your underwear.

 

Is yours also only with light braking and low-to-moderate speed?

As long as it is momentary and doesn't happen with hard braking, it should be tolerable as a quirk of having regenerative braking. I found it quite tolerable in my 2010 even before the recall. The recall reduced it, but didn't eliminate it. (A nearby road resurfacing project eliminated the bumps that had reliably triggered this in my 2010, even after the recall.)

Upsets that occur during hard braking, or without a road bump, or last more than a moment, are a much greater concern. There are hints of such problems, but no apparent critical mass of driver reports.

 

Gen II also suffered from this. It is a common thing on the Prius. Gen III actually does better than the Gen II. If you have driven both of them, you will probably agree.

As stated, it is the ABS working along with the skid control. If you ask me the system is too sensitive. As long as you are aware of it and leave adequate assured clear distance ahead you should be ok at least as far as smashing into someone.

Yes, I do agree it can dirty your britches the first time it happens. Scared me too the first time for sure. Coming down a incline, and turning too. Was using regen brakes and it felt like everyone says, the car took off. But in reality all that happened was the braking was reduced and then came back in once everything settled down. Watch the light on the dash. It will flash when the scenario happens. Crappy tires will make it even worse. It can also happen when turning into a parking lot and go over a bump while you are braking. What most recommend is to simply keep firm pressure on the brakes and soon all will be normal again. In other words "don't panic".

 

It happens ALL THE TIME in my 2011 Prius. I was aware of it before I bought my car and after 3 years am still trying to get used to it. I believe this to be one of the issues that Toyota has been trying to ignore; it came to light back in 2010-2011 (?) time frame when Prius was under attack because of the unusual accidents that were being reported throughout the US. The same accidents that Toyota attributed to (perhaps) lose floor mats. It is amazing that they haven't fixed this fairly serious problem; but hey, look at GM with their ignition switches. I'll just keep buying them with the hopes that in about 10 years, they will address it and fix it.

 

Mine happens with hard braking. At notice it especially if I am braking while running over a manhole cover near where I live coming to a stop at the nearby stop sign it will lunge forward. Also at other locations if I am braking coming to a stop and hit a bump just right it will lunge forward. It is a miracle that I have not had an accident because of it. When you are driving in Chicago traffic you are driving in such close proximity to cars ahead of you that you can not or forget to keep a safe distance all the time to compensate for this and also you have no way of knowing where every manhole cover and bump is located. Your brain will not compute all of this.