What just happened? (Uncontrollable engine surging)

So, I was just driving home from work in my 2005 Prius (~78k miles) when the engine started surging erratically and uncontrollably. I don't know if this is the cause, but I hit a bump right as I was hitting the gas and so I wasn't surprised when it revved up at first. But, then I backed off and it kept revving. Then I took my foot off the gas and it was still revving and accelerating so I had to start braking to keep going the same speed.

It kept erratically surging and then letting off as I basically kept braking at different levels to maintain speed or slow down when I could as we were coming to an intersection. The light turned red and I managed to get to a stop even though it was still revving, so I hit the P button and the engine calmed down. So, when traffic started again I slowly put it back in D and it surged again. We didn't move much before we had to stop again so I put it in P again. I noticed the battery icon was down to a few pink bars so I turned off the radio and air. Traffic started again and I put it in D and this time it seemed ok. I detected a faint smell that I think was probably from the brakes/tires being overheated, but it could've been something else maybe. It drove normally the rest of the way home.

I'll have to see if I can find a shop here to take a look at it, but in the meantime does anyone have a clue what happened and is there anything I can do to prevent it from happening again?

 

There is no way anything could've hit underneath. It was maybe a 1" lip or something. Right when it started I saw some yellow indicator light, but I was so frantic I didn't really focus enough to see what it was and it went away pretty quickly.

 

I've owned it for about two years. What happened to me doesn't really sound like what you are describing. The engine was definitely surging as if it was full throttle or no throttle for a good 60-90 seconds until I got it into park. The brakes were working, but I just had to push them really hard to fight against the engine when it was surging to keep from accelerating.

 

I don't think I'm the only one as I found other similar reports online. Some indicated the traction battery could be going bad and others said something about "resetting the delta history" possibly fixing it.

I've only lived in this country a few months and I brought the car with me so I've never actually been to the dealer here. I'll try to get an appointment to go this weekend hopefully.

 

It does have floor mats. They seem to be designed with a cut-out on the accelerator side so they don't even go under it. It can't really slide forward as the left side goes all the way to the back under the brake pedal. Also, it looks like both pedals are around 2" above the carpet and connected from above not through the floor. I tried to force it to slide and it won't slide, but I can pull it up and out.

Thanks for the thought, but I am thinking this isn't the cause. The way it surged to basically full throttle and the zero throttle (since my foot was off the gas) several times makes me think it must've been some electrical/computer issue. I drove it just a bit early this morning before there was any traffic to see how it did. It drove fine, but I did notice that the instant fuel efficiency readout thing was reading the worst possible at 99L/km when I was stopped. So, the ICE was running even though I was sitting still and the battery readout was a little over half (It's below freezing, so maybe it runs the ICE for heat anyway?). As I started moving obviously it changed, but it was still really horrible and the little animation would show energy going to the battery when I was braking but none coming out of the battery at all. The battery level kept going up until about 2 bars were left and I was starting to get a little worried about what might happen if the charge got too high, but then I noticed it started showing energy coming back out of the battery and the fuel efficiency went back to normal. So, maybe I was just being overly paranoid this morning and maybe it was just something with the temp or something (I haven't ever driven it when it was below freezing before so I'm not sure if maybe it does rely more on the ICE for heat or anything).

Maybe the thing the other day was just a glitch, but hopefully they'll be able to find a record or something of it when I get it to the dealer and they hook it up to their computer or something.

If they find something I'll post back here and let everyone know.

 

I take back what I said before. It finally got warm enough to drive again so I took it on a long straight road with no traffic and floored it again. It only hung up for a second, but it did hang on the edge of the floor mat. Looking at it I didn't see how it would be possible since the floor mat has that big cut out under the gas pedal, but that's precisely why it was able to catch on that edge.