Toyota gas pedal problems

In other words, why didn't they implement the system to fail safely.

I agree 100%.

You know, there's a reason that air brakes work the way they do--with the air pressure holding the brakes OFF, such that if the air pressure fails, the brakes are ON.

Fail safe. It's a good idea.

MoPar Man wrote in news: snipped-for-privacy@Man.com:

I'm not sure there are many new cars that use throttle cables anymore.

Electronic Stability Control (ESC) and Traction Control (TRAC) effectively require that the PCM have full control over throttle openings. A mechanical cable makes ESC and TRAC harder to implement.

ESC seems to be universal now:

If the sensor is faulty, the system's fail-safe defaults to idle.

There is no problem with the sensors themselves.

That's what's happening. The new metal-bar fix prevents the stickiness.

That's hard to square with reality.

That a look at the picture on Transport Canad'a website regarding this issue:

No spring would lift /that/ pedal, I think.

Toyota is changing the PCM programming to kill power if the brake and gas are pressed at the same time.

My thinking? People with winter boots or with big feet will accidentally hit gas and brake at the same time in traffic and end up getting rear-ended. I'm not sure Toyota can win this one no matter how hard they try.

The claim is that there is a binding in the mechanism that prevents the return spring from returning the pedal in the desire manner. I've seen an illustration of the piece that they are adding to correct this issue, but I can't understand how it will fix the problem. I am hoping to get a good look at a "repaired" unit.

It is my understanding that Toyota is going to implement this sort of fail safe system at least on some cars.

Ed

Feds look at Toyota electronics as source of acceleration defects

February 2, 2010 - 4:21 pm ET

WASHINGTON -- The U.S. Department of Transportation is looking into whether Toyota Motor Corp.'s problems with unintended acceleration can be traced to defects in the electrical controls rather than just the mechanical problems cited by the automaker, a Transportation official said today.

"We're not finished with Toyota and are continuing to review possible defects and monitor the implementation of the recalls," Transportation Secretary Ray LaHood said in a statement.

When asked whether the federal review includes possible electrical problems with Toyota vehicles, a Transportation official who asked not to be identified responded in an e-mail, "Yes."

Toyota spokesman Jim Wiseman could not be immediately reached for comment this afternoon about the expanded federal review.

Since announcing its recalls and a production halt last week, Toyota has maintained that problems with unintended acceleration were limited to floor mat interference and sticky accelerator pedals.

Shinichi Sasaki, Toyota's vice president in charge of quality, today denied accusations that electronic malfunctions were contributing to the reports of unintended acceleration.

"We have not come across any case in which we have found a malfunction," Sasaki said in an interview in Japan. "But if any additional reports arise, we will conduct testing using all technology at our disposal."

Also, in a full-page advertisement that ran in many U.S. newspapers today, Toyota Motor Sales U.S.A. President Jim Lentz said: "We have launched a comprehensive plan to permanently fix the vehicles we've recalled because in rare instances, accelerator pedals can, over time, become slow to release or get stuck. We know what's causing this and what we have to do to fix it."

But Safety Research & Strategies, a consulting firm, said in a posting on its Web site: "Neither floor mats nor sticking accelerator pedals explain many, many incidents" of unintended acceleration.

FWIW, one thing that aggravates stuck accelerator type problems in any vehicle that powers the brake booster with engine vacuum (98+% of all passenger vehicles) is that when the throttle is open much above the idle position, the engine vacuum to the booster is almost nil, so once the initial booster charge is depleted (typically happens with the 2nd or 3rd stab of the brake pedal), the brakes are almost useless against the pull of the engine.

You can see this for yourself in your own vehicle - with no other traffic around and at cruising speed, simultaneously push on the brakes and the accelerator - while still pushing the accelerator (you don't have to push the accelerator very much to see this effect), release the brakles and apply them again. You will be amazed at how ineffective the brakes are. Again - it is not due to the engine being that more powerful than the brakes normally are - it is due to the vacuum not being available to re-charge the booster once the initial couple of stabs at the brakes has occured.

Yes, this is true. I had a manifold vacuum gauge on my '65 Dodge and could watch the vacuum change depending on my speed and gas-pedal behavior.

I thought there was some sort of design rule (if not gov't regulation) that a car's brakes must be able to hold a car in-place regardless how powerful the engine was. Presumably this test would be performed from a stand-still. In these cases of run-away Toyota cars, it's understandable that given a car that's already going 30 - 60 mph with an engine running wide-open, that the brakes simply can't overpower the inertia the car already has plus the power being delivered by the engine (and combined with almost no vacuum boost assist).

A USA-today article from last week mentioned the mindset behind this faulty computer-control situation is that the computer is programmed to not judge what the driver's intentions are if it seems that both the gas pedal and brakes are being applied at the same time. I think that's a coward's way of explaining it.

One possible (but un-voiced) explanation is that someone has the patent on having the computer reject the throttle-position sensor when the brake is depressed (and it would cost a fortune to license it). Another explanation is that it might result in a *lower* level of liability against Toyota if it simply kept building cars with the same faulty control pattern programmed into the computer instead of introducing a fix for newer cars while leaving existing cars alone.

Today on the web I read an article showing in good detail exactly where these pedals are sticking. It looks like 5 small teeth mesh with each other (3 on the stationary fire-wall side, 2 on the moving pedal) and if the pedal is pressed hard enough, these teeth end up sticking together. The proposed fix is a metal bar that acts like a stop to prevent these teeth from meshing to the point where they bind up. There appears to already be a stop that's built into the mechanism, but it's smaller (and shorter) than the proposed fix.

(I have no idea what the teeth are for - perhaps they are part of the actual position sensor? Sensing electrical resistance as a function of meshed area? Or perhaps optical?)

The article went on to explain that many German cars have the correct computer programming (ie - brake over-rides the throttle sensor). Some hi-end Jap cars might also have this. My theory is that if the car is expensive enough to indicate that the owner has enough $$$ to sue in case of injury, then the auto maker programs the brake over-ride function into the computer.

There is one possible reason have the throttle pressed down while riding the brakes - that's if you're stopped in traffic on a hill (facing up) and you don't want to drift down and hit the guy behind you when you take your foot off the brake. In that case, if you take one more sensor measurement (vehicle speed as measured by the transmission output speed sensor) then you can develop a set of rules as to when to over-ride the throttle sensor and when not too.

In that situation, presumably you're starting from a stopped position, you get a green light and you take your foot off the brake and shift it to the gas pedal, where you come down but end up hitting both pedals. Your brake lights blink for a split-second, but they'll still be red, you won't advance very far (because your pressing on both pedals) and the guy behind you won't get the impression that you're moving to the extent that he's going to start moving and run into you.

My 2005 Subaru Forester had drive by wire. Never had a problem with it, nor do I know of any similar problems in other Subie models.

Our 2002 Isuzu Trooper has this sort of system. I'm guessing it was relatively new at the time as I recall seeing it mentioned as being a "feature" or whatever. I've never heard any reports of problems with the system... I'm guessing it was used in all the 98-02 models.

Interestingly enough, there was a recall on our 94 Trooper a few years back for an issue with the throttle sticking - and it's a "traditional" throttle.

I think a lot of the new cars are indeed going with a "drive by wire" system. I'm nearly positive that is how it works on the 05 Grand Marquis we have as a company car at work...

Wesley

In message , Wesley writes

Drive by wire has to be just about standard here in the EU as emissions are tightening every five years or so and ordinary injection whether mechanical or electrical can't cope, so everything has to be controlled by a pre-mapped microchip. It's not more unreliable than a straight forward cable, remember the Ford Explorers with the sticking throttles, which turned out to be a fault with the cruse control cable holding both venturi of the carburettor fully open against the drivers wishes. (See Youtube.)