Toyota throttle assembly and metal shims and tools used for recall repair
Toyota throttle assembly and metal shims and tools used for recall repair. Click image to enlarge

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By Jim Kerr; photos by Chris Chase

Toyota’s recent vehicle recall for sticking throttles has been making big news. I don’t want to make light of those who have had accidents because the engine wouldn’t slow down, but this situation isn’t new. Sticking throttles have occurred for decades and with all makes of vehicles, and some have had more problems than others – remember Audi? The company almost ceased to exist in North America because of unintended acceleration complaints back in the mid 80s with their Audi 5000 models. Others had lesser problems too. Knowing what to do if a throttle sticks can make the difference between an accident and simply pulling over safely to the side of the road.

First, let’s look at what they say may be causing the Toyota problem. Initially the gas pedal was deemed to be sticking because the floor mats were catching on the pedal. They quickly advised customers to remove the floor mats while replacement mats were being produced that would be held securely in place. This problem isn’t unique to Toyota. I have driven thousands of cars with both factory and aftermarket floor mats and if the driver is not careful, the mat can be pushed forward where it could interfere not only with the gas pedal but in some cases with the brake pedal too. Fortunately, most original equipment mats now come with retainers that help keep them in place, but I often see these not being used. It’s a simple matter to put the mats back in properly after vacuuming the interior.

Toyota throttle assembly and metal shims used for recall repair
Toyota throttle assembly and metal shims used for recall repair. Click image to enlarge

Next, the Toyota problem was linked to the pedal assembly not returning all the way to the closed, or rest, position. A modification to the assembly provided by Toyota is designed to prevent this. The percentage of vehicles that are actually affected by the problem is very small, but because many Toyota models use the same assembly, many vehicles are on the recall list. You would likely never have a problem with your vehicle, but its better to be safe than sorry.

Gas pedals on almost all new vehicles are connected to a variable resistor instead of being physically connected to the engine throttle plates. The computer sees the electrical signals from the variable resistor assembly and then operates the motor on the throttle to open the throttle and accelerate the engine. While a fault in the electrical system could theoretically cause the throttle to open incorrectly, more than one signal is used to determine throttle opening and if any signal is incorrect, the default is to shut the throttle.

Throttles used to stick before computer controls came along: a drop of frozen water on a throttle cable would cause it to bind; worn throttle shafts could allow moisture in and freeze the throttle plates open; a throttle return spring could break or become disconnected, preventing the throttle plates from closing. These used to be common enough occurrences during the 50’s and 60’s that driver trainers used to even discuss sticking throttles during class and how to deal with them.

Toyota throttle assembly and metal shims used for recall repair
Toyota throttle assembly and metal shims used for recall repair. Click image to enlarge

So what should you do if the throttle sticks open on the vehicle you’re driving? The first rule is don’t panic; you have several options. Toyota recommends placing the transmission in neutral and pulling over safely to the side of the road. The computers for modern fuel injected engines limit the engine rpms, typically to about 3,000 to 4,000 rpm when the transmission is in neutral. It may sound like it is revving high, but it is safe. After pulling over, you can turn off the engine.

Most drivers automatically try to stop the vehicle with the brakes. The brakes will work, but there is less engine vacuum available with the throttle open so any vehicle with vacuum-boosted brakes (which is most of them) will have less brake assist. It may feel like there are no brakes, but that’s not the case; shifting to Neutral helps here.

You could turn the ignition key off, but there are dangers here. First, with the engine off most vehicles lose their power steering. There is still manual steering, but it will take more effort and you need to be prepared. Secondly, if you turn the key too far, it could lock the steering on some vehicles. Most vehicles have an interlock that prevents the steering from locking unless the transmission is in park, but not all do. Simply turn the key to the off position – not to lock – and be prepared to use manual steering and brakes while coasting safely to a stop.

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