The somewhat recent thing about runaway Toyotas seemed to bring the issue of unintended acceleration to a real head. My personal opinion is that while it can happen (worn cable, sticky throttle plate, faulty IAC which may be due to neglect) or even an electronic hiccup on a rare occasion I’ve always thought that most were due to the mind and feet not being on the same page.
I recently finished a book by Ben Collins. Those familiar with the BBC show Top Gear may know him as The Stig, their in-house race driver. The man is a genius with a steering wheel and also trains the various celebrities who run laps around their track.
Collins states that he takes them out and show them the ropes followed by riding along as a passenger and offering advice while monitoring their driving technique.
He said that some celebrities are calm and collected (Simon Cowell is one) but that a number of them have a bit of anxiety or with or even fear. This gets to the point about unintended acceleration.
Collins stated that some of them were insisting they were braking even though they were actually depressing the gas pedal while he watched their foot action and saw this was not the case at all. He also stated that he believed this to be the cause of many traffic accidents and I would agree with him.
Anyway, just thought that was an interesting comment in the book and could provide some insight into those people who swear to the bottom of their souls they were braking and did not touch the gas.
I have always felt that this mistaken pedal identity was the common thread in the vast majority of SUA cases.
In fact, many of these “victims” have apparently said the same thing–along the lines of “the harder I braked, the faster the car went”.
I had almost forgotten about that classic line until about 4 years ago when I was a passenger in a car that was T-boned as we were about to exit a gas station. The woman driver, who hit us broadside with her Lexus Rx-330, told the cop, “the harder I braked, the faster the car went”.
We were actually the second car that she hit. First, she rear-ended a Ford Escape on the highway, then as her car went even faster, she steered off of the highway, entered the gas station property, and totalled my friend’s Accord sedan. At the insistence of the police, her car was examined by a master mechanic, who pronounced both the brakes and the throttle action of her car to be functioning properly. Mr. Collins’ theory was proven correct once again, I suspect.
I agree the 99%+ of unintended acceleration is driver error, but given the number of inputs for sensors, and given people make mistakes and programs are written by people, it’s possible that given just the “right” inputs you could get unintended acceleration. It would take some strange circumstances for this to happen, but a little stray voltage, and sensor(s) that’s has a wrong reading, especially those that rest on start up, you could setup a situation where you could get unintended acceleration that would disappear once the car is restarted. But that would be very few and vary far between.
I don’t think it was a pedal identity error with the Toyota problem, especially considering the fix they installed. It only affected Toyota’s with the electronic throttle and they put a little hardened plate in the bottom of the gas pedal module. What I believe was happening was that they drivers involved were chronic, pedal to the metal types of drivers and they put a dimple in the bottom of the gas pedal module. Eventually the pedal would stick at full throttle. Why else would a hardened metal plate fix this problem?
I always thought trying to figure out whether unintended acceleration was due to driver error or mechanical/electronic/design malfunctions is kind of like figuring out something like whether or not trees die because of insects. Obviously some trees do. Others don’t. There simply is no leap of logic that can get you from “some cases of unintended acceleration are operator error” to “all (or even most) cases of unintended acceleration are operator error.”
The Toyota conundrum seemed to have been largely an hysterical frenzy. My vocation has caused me to drive more vehicles than most and in my leisure I seem to have driven more than most, also. Some Toyotas seem to have a gas pedal that is somewhat unresponsive in the initial application and startlingly responsive as it is pressed further. And while there is no denying that some drivers may have actually experienced their car’s accelerating as they pressed frantically on the brake many more consciously or unconsciously blamed their mishaps on their car and the hysteria grew like a snowball down a Vermont hill side. And. BTW, I have driven Chevrolets that ran away with me when the engine mount broke and know full well what unintended acceleration is.
I just got a new pair of shoes and discovered I had unintended acceleration while I was braking. This happened twice and then I learned how to place my foot on the brake without goosing the gas pedal, too. All me, no car.
My '02 Ford Escape V6 has a long standing sudden rpm increase problem but doesn’t exactly run away. I have seen it at idle in park suddenly run up to about 1500 rpm and hold there. If I kick the accelerator such as to free a sticky linkage it will throttle up to whatever rpm it peaked at and hold there. It’s not the linkage or the pedal. The only cure I have found is turn off the key and restart. It then behaves completely normally thereafter. The frequency of these incidents is a couple of times a year. It has also happened while driving at highway speeds. Under these conditions you first notice it when you get off the gas pedal to slow down and it will only slow naturally to 40 or 50 or so. You have to slow the rest of the way down with the brakes. There’s plenty of brake power to bring it to a stop in almost the normal distance. You can just barely notice that the engine is fighting you a little. When I notice it on the highway (two occurrences) I now just wait until I get off the highway where I’m going and cycle the engine off and on at the first stop sign I come to. I have mentioned it to my dealer and they said they haven’t heard of this as a known problem, it doesn’t set any codes, and there are no service bulletins. I can’t see how they could possibly trouble shoot a fault that occurs so rarely. I don’t want to let them drive it for six months. I keep it in the back of my mind that if it ever really takes off my fall back is to turn off the key til the engine goes to zero rpm then immediately turn the key back on so the wheel doesn’t lock. I can live with it (so far) but it leaves me unwilling to totally dismiss every runaway incident as a driver error.
I would agree with circuitsmith. A fouled throttle body or Idle Air Valve could cause this problem and that falls into the line of induction cleaning; a maintenance procedure.
In the old days you would have sticking choke flaps, hanging fast idle linkage and so on. Now that problem has been replaced by another.
Thanks guys. I have been following the maintenance book with the dealer and I don’t recall seeing these procedures recommended so it probably hasn’t been done. You are very likely right that some cleaning is in order. The car has 75K on the clock and 11 years on the road.
In my '91 F250 dirt would cause slight but annoying RPM surging when the engine was braking the vehicle and some carb or choke cleaner down the intake while the engine was running helped a lot. I guess this RPM runup could just a more extreme manifestation. I’ll go ahead and try your suggestions on the Escape since it can’t hurt. Will the choke cleaner down the intake do the job? Will it damage the Escape injection system? Or should I take it to the dealer?
Now that I think about it the 250 occasionally wants to idle at 1200 instead of 900 but kicking the pedal brings it back to normal so I ascribed it to something sticking since the truck has 170000 on it and 22 years. I think I’ll do the choke cleaner treatment again to that too.
Still, for the Escape, if dirt is the culprit why would a shutoff and restart cycle instantly and completely solve the problem for many months only to crop up again at some random time to be instantly cured by another shutoff and restart?
Get some throttle body cleaner spray. Carb/choke cleaner might do damage, some tb’s are coated.
It a fairly easy job: disconnect whatever air hose that give close access to the butterfly valve, hold the valve open, spray the cleaner and wipe out with a clean rag.
Unbolt the IACV and spray into the ports.
I’ve seen butterfly valves that only act sticky when the engine is pulling a vacuum against them.
You won’t find this in the manual because not every possible repair is mentioned, and this is repair, not preventive maintenance IMHO.
A runaway throttle is a very dangerous condition and “merits” some intense attention by the manufacturer but the hysteria of the public is not conducive to identifying the cause. If for every bona fide complaint of unintended acceleration there are 100 drama queens and insurance fraud claims finding the problem can be difficult.
