Sudden Burst of Speed

[Fullogas12]

I've had my new 2010 Prius III for about two weeks. I've had something strange happen twice now.

While driving in ECO mode, when letting up from the gas I suddenly have a burst of acceleration. The first time it was pretty minor like the car had slipped a bit on the roadway so I didn't think anything of it. Earlier this evening it happened again. This time is was much bigger as if someone had hit the car from behind. It was big enough to slam my head back into the headrest. There was no one around me so I definitely didn't get hit from behind.

This worries me.

Has anyone else heard of this happening?

I'm going to call the dealer in the morning to see what they recommend.

[HTMLSpinnr]

Did the engine seem to be revving at the time? I used to get this quirk in my Gen II (more of an engine rev after let off vs. a burst of speed though).

[spiderman]

Originally Posted by Fullogas12

It was big enough to slam my head back into the headrest.
This worries me.

I'm going to call the dealer in the morning to see what they recommend.

Scary

I would call immediately and perhaps not drive it at all (Toyota Roadside Assistance). Of course I am pretty cautious.
Hope it is nothing serious,
Peter

[wfolta]

The only thing I can think of is the "surge" from when your wheels slip during regenerative braking. (Rare, but usually experienced under fairly hard braking coming to a stop on uneven pavement.)

What was happening, in more detail? Did you let off suddenly? Had you been accelerating or a constant speed? Did you let off and immediately start braking? Was the road bumpy? Are you a left-foot braker?

The alternative seems unlikely, so I'd definitely take the car in for service if I were you, but if there are a couple of other factors involved that you didn't originally think to mention, it might save you time and money.

[ksstathead]

What was your speed before and after the surge?

[moner]

I sometimes get this surge at a certain point on my commute. It happens going downhill, on a bumpy road, and going about 5km/hr with foot on the brakes slowing to a stop sign. I will feel the car suddenly try to accelerate and I need to push the brakes alot harder to stop the car. I called the dealer and he said it was "normal", something to do with the engine modes transition or regenerative braking? I also noticed a slight speed surge once when I hit some gravel accelerating into traffic. These surges don't feel dangerous yet, more startling, but on a slick road or with pedestrians around it could be scary.

[bwilson4web]

If you have a Garmin GPS nuvi, there is a data record of your vehicle that we can analyze. It is a large file so transfer may require cutting a CDROM and postal mailing:

1. mount the Garmin nuvi with the USB cable.
2. copy GARMIN\GPS\Current.gpx to local system
3. check the size of file
4. copy to a CDROM
5. contact me for mailing address

If you are able to reproduce this problem, clear the "Track Data" and repeat the experiment.

Bob Wilson

[Fullogas12]

I hope I can answer your questions:

1. I was going about 30 MPH. I'd just crested a hill and had been accelerating steadily. I'd just eased off the gas.
2. I didn't notice a reving sound. This makes me think it has to do with the electric motor
3. I definitely felt something like a transmission dropping into gear when the surge hit
4. Was too surprised to notice if there were any warning lights
5. I have the navigation package. Is a Garmin built into the package? If so, I can probably access the info. I can pinpoint it to within 5 or 6 minutes. I'd just gassed up a few minutes earlier so I can get pretty accurate on the time
6. I called the dealer today. They said I could bring it in on Saturday but they hadn't heard of anything like this before

I'll drive the road again in the morning to see if there was anything weird about the road surface there. I don't recall seeing anything unusual about the road.

[sglauberman]

Well I just got a 2010 Prius and during the first week I have had 3 separate incidents of non-threatening sudden acceleration. In each instance, I hit a bump in the road and the car instantly started to accelerate. Pressing the break immediately slows it down but there is certainly a problem. Today when it happened I noticed that the losing traction warning light came on and stayed on even when the car was at a stop. The light went away when I turned off and on the car. Definitely a problem.

From reading other posts here I am getting very concerned. I would like this fixed but it is now seeming like the response from dealers/Toyota will be either it's normal or I am crazy. Could be selling my 2-week Prius soon if that is indeed the response I get from the dealer this Tuesday when I bring it in.

--Steve

[spiderman]

Sure sounds like a glitch in the programming. I sure hope the dealer does something about it. Got to the very top person at a minimum. Call Toyota directly if that does not work out.