Sudden Acceleration - It Happened To Us Today

It Happened Tuesday Dec 14, 2010

Your story sounds like mine. I bought a 2010 Prius about 4 months ago. In other words, it is still under warranty. I was braking for a stop sign when the car shot out ahead. The dealership is stonewalling. I'm thinking of contacting my state attorney general. I had come back to Toyota & the particular dealer. I guess it was a bad idea.

Was your situation ever settled? Do you have advice for me?

 

Thanks, Annbrit. No, I never filed a complaint. I was so sure I was pressing the brake but I am mid-60's and decided there was no way to prove it. Fortunately I have not had a repeat and I have gone to dealer for any recalls they suggested. One was for replacement of the accelerator pedal but I have always wondered if there was a software change done at the same time. Bottom line, I can't prove anything but am still a little nervous driving my 2008 Prius. I do not trust the dealership to look out for my best interests since they tried to toally rip me off on a previous car purchase. I wish you all the best.

 

It was not acceleration, it was a decrease in deceleration (jerk, 2nd order derivative of velocity).

Go find a pothole and lightly brake over it, you will experience the same thing. In no way is it dangerous, it is an effect of the regenerative braking. Humans have a hard time feeling the difference between jerk and acceleration since we train ourselves to subconsciously lean "into" acceleration/deceleration.

Borrow an accelerometer and repeat the experiment and it will prove it empirically to you.

 

Annbrit

In case you hadn't read through then entire 7 pages of posts (and I don't blame you if you didn't), Tom explains it pretty well here. I've had the same thing happen to me too (once), felt like I had hit a patch of ice, by the time I had processed what was happening the event was already over.

 

This is the ABS kicking it where you experienced a moment of the system pumpking, therefore losing brake pressure for a moment. The ABS system does this to prevent the wheels from locking.

Your dealer is correct -- there's nothing wrong with your car. This happens to ALL cars, not just the Prius.

 

This is separate from abs pumping. This is due to the regenerative force dropout leaving you with only friction brakes like every other car in the world. All vehicles with regenerative brakes (including the Toyota FJ Cruiser I believe) "suffer" from this phenomenon. If humans weren't so easily deceived by their own sensory systems this would remain a non-issue.

 

I have to disagree, it can be dangerous if you have estimated that you will stop at a distance ahead using current pedal braking force and have to suddenly re-adjust.

It is a design flaw, that scares me and I am neither old, nor having issues with my reflexes, nor a Prius newbie.

Toyota should correct it.

 

If they used the friction brakes instead of the regen it would fix it and greatly reduce the mpg this car can get. I have had it happen a few times in 30,000 miles of driving. it doesn't bother me but if i tailgeted people and waited till the last second to stop it would be a problem for me but i don't. If it bothers you get another car that is not a hybrid problem solved.

 

i don't think it can be 'corrected'. i have had plenty of cars do this with the abs, but when you throw in regenerative braking on top of it, it just makes it feel a little funnier. but i think your sensory system, when you feel the lurch, makes you step on the brake harder which is the right thing to do.

 

The part that scares me is that I am on the road with drivers that can't cope with something that simple.

 

No, its working just fine, You however, need to redefine you ideas of stoppng distance, reaction time, and your habits in driving the car.
You bought a new vehicle, learn it's systems and how they effect/affact you!

I did, I'm good with it!

 

I have read most of this thread with dismay because of how unsympathetic and arrogant many of you are. It points to a problem that I have obsreved in this newsgroup which I can only describe as narcissistic elitism. Give these people a break. Let them work through the issue with the dealer and I am sure that they will let us know what the resolution is. Remember the Prius is both a car with a computer and a computer with a car. The fact that it hasn't happened to you in 80000 miles is irrelevant. Thank your lucky stars it hasn't. Anybody that has bought, built, manufactured, or used electronics knows that intermittent problems plague every device ever made. There are a ton of interconnects, ground connections, wires, shields, pc boards, microprocessors and buses in this car and probably gigabytes of software. You can't test everything so software bugs, EMI responses and intermittent connections are bound to happen. Conjecture, though rampant in this thread has no place. You are only guessing and you don't have the data to generate a rational, meaningful response. Give 'em a break and let's see what they and the dealer come up with before we pass judgement. God forbid we might find out something that saves a dented fender or worse.

 

I have driven my 2004 Prius 187,000 to date and the braking hesitation (as others have said it is NOT acceleration) has happened to me a few times. Since the immediate reaction is to step hard on the brake, the friction brakes take over. If the situation was caused by a large slippery patch the ABS will pump the brakes maintaining directional control but lengthening your stopping distance.

If this puts you and your Prius at risk you were "following too closely" (or took a risky lane change) for the conditions (ice, sand, gravel, ...) and are subject to the "blame" for the accident.

Our Prii are not perfect. Nothing that man designs can be perfect. I am more concerned with the so-called traction control (it is there to protect the drive train from sudden changes in torque) which makes our Prii lose power, typically when trying to merge into traffic. This has made me very conservative when turning into traffic (I don't want to be broad sided).

JeffD

 

If you own a Prius, please sell it.

 

It happened to me last week when a pedestrian police officer stepped quickly in front of my car as I slowed to go around a corner.

I was not tailgating. I had no choice but to wait till the last second and the cop was unnerved (but polite) about it.

I've been a Prius fan, owner, driver since early 2007 (on my 2nd) and I still think it's a great car and would buy another, but there are circumstances where the lack of deceleration IS dangerous.

The thing that bothers me most is that it seems like the 2010 V-AT does it a lot more than the 2007 Package 6 did.

 

Find a wet, smooth manhole cover like I did on the way home and feel the sudden burst of acceleration. :madgrin:

 

Many of these problems, real or otherwise, are well documented and well understood. Just because they are new to you and other new members of the forum does not mean that they are new to many of the old guard Prius drivers. Your rush to judgment is at least as egregious as that for which you rail against. Perhaps you should take a small dose of your own advice and give the experienced posters a break as well.

Tom

 

This isn't a special education class we are discussing. It's real life with real cars that can kill people. Patting someone on the head when they don't understand how the brakes work does no one any good.

 

I agree. Every car has different driving characteristics. Operators of such need to be familiar with their equipment either by means of training, defensive driving, or simply, being open minded by listening to others on the forum!

Some vehicles drive alike, some do not. The Prius is not your conventional vehicle. It is a mass produced hybrid that incorporates many new and technology and design.

Cars are different from each other. The Prius is very different. You need to know the limits of what you are operating!

Ask any pilot, sailor, or someone that operates any sort of high-tech equipment and he/she will tell you the same.

Some people just have no business behind the wheel.

 

"In Prius when you are braking lightly (regenerative braking), it is a fairly common experience to feel a momentary surge if you hit a pothole or go over a manhole cover.

I have experienced it multiple times. It is quite possible something similar may have happened. It is unnerving first few times you experience it for sure.[/QUOTE]"

I've experienced this momentary battery surge when going over small bumps even if my foot is NOT lightly on the brake, and wondered if this can be fixed. My battery also make a quite loud (to me) buzz sound when braking or accelerating. Is this normal? And my car, which I just got, a 2008 package 3 with 67,000 miles, doesn't ever seem to want to be in stealth mode, except when stopped. Is this normal? I'd LOVE to drive at very low speeds with ONLY the battery!!!! THANK YOU!