Prius - sudden acceleration

My mother’s Prius has experienced the sudden unintended acceleration several times - each time, fortunately, it was a “lurch” rather than the nightmare extended “wide open throttle” we read about in this morning’s Chicago Tribune, which has a picture of a crushed Toyota that accelerated off a cliff into the Pacific Ocean. My mother is of course terrified, talking about buying a Ford plug-in car, because when she took her Prius into the dealer last May, after the car lurched into the bushes and needed the body shop to restore the hood - they looked at her like it was her fault. Folks, this is not “floor mats” - the floor mat in the Prius does not wrap around the accelerator pedal and there’s no way it caused the car to suddenly accelerate. The only helpful information in the Trib article was from the guy who said he turned off the power on the car - with both feet slammed on the brakes and the emergency brake on - turning off the power was the only thing that finally stopped the wide open throttle. Any advice from Tom and Ray - or from anyone in your wonderfully resourceful audience - would be greatly appreciated. We count on the Prius too much not to be completely afraid this will happen again.

Turning off the engine will make steering and braking very difficult. The first thing to do under these circumstances is shift the transmission to neutral.

Shifting to neutral will allow the car to be steered and braked safely, even if the throttle is stuck open.

Why fight the engine?

PS - Ford doesn’t make a “plug-in” car.

shift into neutral - is what we will do. thank you!! I will break the news to my mother about the “no Ford plug-in” . . . she loves the low-carbon-footprint of the Prius - if you were looking for a safer alternative to the Prius - what car would appeal to you?

I’ve read posts here about unintended acceleration in a other Toyota vehicles, but this is the first time I can recall reading about it regarding a Prius. There are an awful lot of these vehicles on the road. If this was a common problem it should show up more often.

Having said that, if your mother doesn’t feel safe she won’t enjoy driving the car.

Honda recently re-introduced the “Insight” hybrid model, and this time it’s a four-door looking very similar to the Prius. The Insight is a bit smaller than the Prius, and can’t run on batteries only, but it is a viable alternative.

The Ford Fusion hybrid is another possible alternative to the Prius. The Fusion doesn’t announce itself the way a Prius or an Insight does, but it’s a decent hybrid vehicle. Perhaps this is the Ford to which your mother was referring.

your thoughts are really helpful, thank you so much. I will talk to my mother about this. she’s 82 - when the dealer looks at her like she drove that car into the bushes it has terrible implications about her freedom - her first reaction to the Trib article was relief that this is clearly a legitimate problem. on the other hand, that car has lurched several times for her (hasn’t happened when I’ve been driving, but I drive it much less than she does). she’s the kind of person who couldn’t trade the car in knowing it isn’t safe, so her next step is complicated! I’m going to suggest to her that we go to the dealer together, make them inspect the whole acceleration system very carefully. thank you again!

You just might want to park that Prius.


I think it’s important to keep in mind that something like this is possible with any vehicle using a drive-by-wire throttle, and there are LOTS of vehicles on the road with drive-by-wire technology. Some manufacturers even advertise it as a selling point.

What drive-by-wire means is there’s no mechanical linkage between the gas pedal and the throttle. The computer reads an electrical signal from the gas pedal (along with many signals from other sensors) and actuates the throttle on the engine electrically.

If the computer gets a faulty signal from any component it could decide to open the throttle even if this is not desired by the driver.

Conversely, the computer could decide NOT to open the throttle, regardless of how hard the gas pedal is pushed. You don’t hear about this problem because it doesn’t result in runaway vehicles.

All manufacturers claim that these drive-by-wire systems are extremely reliable, which they are.

But so is the Space Shuttle.

Nothing is 100% reliable.

The correct thing to do is to put it into neutral, as other posters have said. Considering her age, it would be a good idea to go to a parking lot and practice doing this a few times so that she won’t be flustered if she has to do it in real life.

I think you at least have to consider the possibility that this is operator error.

The age of the driver, the fact that it never happened to you when driving it, makes it entirely possible the gas pedal is being mistaken for the brake. A few decades ago, there was a similar concern regarding Auids…that was traced to mistaking the gas for the brake.

The only helpful information in the Trib article was from the guy who said he turned off the power on the car - with both feet slammed on the brakes and the emergency brake on - turning off the power was the only thing that finally stopped the wide open throttle.

Again, the fact that BOTH feet on the brake didn’t stop the car suggests the feet weren’t actually ON the brake…any modern car’s brakes ought to be able to overpower the engine (particularly a Prius’ engine) in a similar situation.

operator error - that’s what my mother thought, when the car rammed into the bushes. this is a woman who’s never had an accident - never even a ticket in more than 60 years of driving. the thing is, this has happened several times in different circumstances, and there’s some fairly appalling evidence of what would happen if she had been driving at highway speed when the car chose to open its throttle. I am encouraged by the responses on this discussion board - I think we can take the Prius to the dealer and ask them to check the electrical systems and computer thoroughly, look for any kind of anomaly - and if they find one, fix or replace the systems. I’m well advised by mcparadise that lots of cars use this technology with no problems ever, but if the Toyota people aren’t able to find/fix whatever caused the problem in my mother’s car - we may have to treat the Prius as “local errands only” and rent a car for our next road trip.