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What Might Cause a Gas Pedal to Become Stuck?

Toyota, the world's largest automaker, has suspended sales of certain models and recalled millions of older ones as its engineers search for the elusive source of a sticky--and dangerous--accelerator problem

During the past few days, Toyota Motor Corp., has taken the unprecedented step of halting sales in the U.S., Europe and China of some of its most popular car and truck models. The reason: potential defects that cause the vehicles to speed up without warning and run out of control. The move follows a huge (and growing) recall of older Toyota vehicles last week. Safety Research and Strategies, based in Rehoboth, Mass., has reportedly implicated the sudden unintended acceleration problem to 2,274 incidents in Toyota vehicles, causing 275 crashes and at least 18 fatalities since 1999.

The maker of the suspect pedal mechanism, CTS Corp., of Elkhart, Indiana, is working with the carmaker on a revised design to remedy the problem, Toyota says. Pedals featuring the revamped design are now in full production at CTS. Meanwhile, the companies are field-testing modifications to existing pedals.

Jake Fisher, senior engineer at the Consumer Reports Auto Test Center in East Haddam, Conn., provides some independent insight into the vexing safety problem that threatens Toyota's hard-earned reputation for quality and reliability, and, ultimately, its bottom line.

[An edited transcript of the interview follows. ]

What's causing some Toyotas to accelerate unintentionally?

Truth is, nobody really knows. There are all kinds of theories—floor mats that ride up to depress the accelerator pedals, frictional wear in the brake mechanism, defective electronic controls, electromagnetic interference. Certainly, Toyota is not clear about the cause; it has already released three successive announcements, each of which claims that it has figured it out. The root cause is probably the culmination of many things. Keep in mind that this is a very rare occurrence that is intermittent in nature and is not easily repeatable, so evidence is hard to find.

How rare is the problem?

The number of relevant complaints in the logs of the National Highway Traffic Safety Administration [NHTSA] is tiny considering the number of vehicles on the road. So people certainly shouldn't go park their Toyotas for the duration.

Have other automakers encountered the stuck-pedal issue?

Toyota is not alone. Although about 40 percent of the NHTSA complaint data concern Toyotas, every other carmaker is represented, as well.

Toyota initially reported that the floor mat was the culprit, as it could slide up and obstruct the accelerator. Why would Toyota mats be different from those of other automakers?

At most dealerships vehicles come with the mats installed, but in my experience Toyota offers them at the point of sale as an extra. The buyer has two choices: fork over 150 bucks, or go to a Pep Boys or other auto parts store. In the first case the dealer typically throws them into the car or the trunk, so the mats don't necessarily get hooked into the floor correctly. In the second, the mats may not fit or be installed properly. Either way, the mats can interfere with the operation of the gas pedal.

Are there any other suspects not related to floor mats?

The electronic throttle control—the digital fly-by-wire unit that links the gas pedal to the fuel delivery unit. Unlike some manufacturers such as Volkswagen and the other German carmakers, Toyota has yet to implement what's called a smart throttle. It's a software algorithm that allows the brakes to override the accelerator.

Toyota issued a statement last night that said there might be a "rare" problem related to premature wear in a common gas pedal part that could lead to unintended acceleration. What should Toyota engineers be doing to the fix the problem?

The only thing they can do: conduct thorough forensic analysis and testing on the affected vehicles and all of the throttle components to evaluate every possible explanation as quickly as they can. I can't imagine how terrified they must be of losing their reputation for quality.

What should a driver do in the event the gas pedal gets stuck?

First, hit the brakes firmly. Then put the car in neutral without taking your foot off the brake. The engine is going to rev higher in response, but bring the car to a full stop safely and turn the engine off. You need to make sure that you don't release the brake because power brakes work off [engine] vacuum, and you don't build any vacuum when the engine throttle is wide open. As soon as you lift off the pedal, you've lost all your vacuum power-assist, and your brakes get very hard and stiff.

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