Unintended Acceleration - Find the Cause

ninjataco

I'm a little late here, but just found out about this contest from Episode 8 of Revisionist History.... I hope this is still worth posting.

I recently experienced "unintended acceleration" and wanted to share my experience/findings. It wasn't driver error. My immediate reaction was to disengage the clutch and put the car in neutral. I hit the rev limiter almost immediately and, I'll admit, was in a little bit of a panic at this point. I managed to shut the car off by the third time the RPMs dropped and I slowly rolled to a stop.

Fortunately, I was on a fairly straight back road with no traffic. I pumped the gas pedal a few times with the car still off and everything seemed to feel fine, so I turned the car back on and drove home. I had no explanation at this point for what happened, and nothing I tried on the rest of the drive home seemed to get it stuck again.

It's not a daily driver, and so I don't remember if it was the next day or a few days later that it happened again. I was backing out of the garage and much more calm this time; I shut it off by the second time the RPMs hit the limiter. Since I was still in my driveway I got out and was determined to figure out what it was. My DD is a Toyota, so I'm sorry to admit that floor mats did cross my mind :-(

Didn't seem to be floor mats in my case, but I had recently removed the cruise control actuator. There is a cable that connects to the back of the gas pedal and sort of "pulls from above" on a lever that is mechanically linked to the gas pedal. It is quite easy to slip the cable out of its plastic clip, and then it slides through the firewall (after I broke the clip holding it there) and comes out with the rest of the part I was trying to remove. I was aware of the lever still attached to the pedal, but didn't think much of it since it had been there the whole time. When I was uncomfortably positioned in the foot well doing the work - and I think this is the key problem in my very specific case - I also tried to "neaten up" some of the mess that I found under the steering column. I had taken the driver seat out to do this, and this was the first time my head was this close to the pedals. There are two plastic boxes under there that look like they are supposed to clip under the steering column. They are labeled as air bag components and so I thought I'd better not just disconnect them to see what happens. I managed to get them back up to where it looked like they were supposed to be, but it was a tight fit. The previous owner had some remote box in there too that I did remove, but I guess my point is that not all the wiring was stock. This is where I found the problem: Where I had positioned the air bag power supply was (in hindsight dumb on my part) pretty close to where that lever was for the cruise control, ABOVE the pedal. I could see that the bent end of the lever (the part that held the cable) was sliding along the side of the blue plastic box. Since the lever moved with the pedal, I was able to push it past the end of the box and that's where it hooked. The pedal wasn't all the way to the floor to do this, but it did seem like the circumstances needed to be just right. I couldn't get it to hook all the time, sometimes the clip end would just slide back over the corner of the box and no problem.

I let the power supply box hang down again until I could figure out a better solution, but that was definitely the problem in my case. I did a little research and my car is not the only car that has this particular design. Not all cars have it, but it doesn't seem to be uncommon for cars built in the same year (1993). I had removed the CC cable, but from what I saw I bet the problem could still happen with it attached. The box-in-the-way was the real issue in my case and so maybe you'll still call that "driver error" :-P I just wanted to present another side to this that wasn't just me stepping on the wrong pedal, thanks.

gthomasbaldwin

Long story short, you broke the car.
Actually in your case it wouldn't be driver error it would be mechanic error, I think.

Gladwell's podcast was interesting. Nice mention of Edmunds.

andres3

People sometimes forget that incompetent workmanship can end up killing people.

ninjataco

It wasn't incompetence, I was actually fixing the mess that was there to begin with. I'm just trying to point out that this lever can also get stuck on things, and not just the pedal itself.