Unintended acceleration SIMULATION results:

NO loss of power steering; NO loss of power brakes; NO loss of power steering when the ignition switch was turned to OFF at60 mph, and gear shift left in DRIVE.

Car slowed to 30 mph, and the engine restarted when the ignition switch was returned to RUN. The car, of course, returned to maximum acceleration; but, turn the ignition switch OFF, and was able to slow, again.

With the ignition switch OFF, the RPM and Speed gauges go to 0 (zero) INDICATION; but, that was because electric power to them had been cut; and, the air bag light came on.

When the ignition switch was returned to RUN, the gauges resumed to indicate, and the air bag light went out.

To have the THROTTLE STICK WIDE OPEN, and to turn the ignition switch OFF, and STILL have power steering and power brakes, disputes the notions frequently expressed by so called “experts”. Those contentions are, evidently, wrong for a car whose engine is still being driven by the moving car. So, as long as there are power steering and power brakes, at least to a low speed, the car can be brought to a safe stop.

The other commonly held ‘truth’ is the ‘you’ll lock the steering if you’re not careful when you turn the key’ statement. But doesn’t the car have to be in park to do that? Seems like locking the column would be very hard to do.

The steering wheel does NOT lock in any gear except Park. This fact shows the myth to the contrary, to be false. That make three dead myths, doesn’t it?

I will have to add - my park interlock went out on my car at one point (since repaired), and I could remove the key while in ‘drive’, so for that small group of cars needing the park interlock repaired, it could be a problem.

To turn the ignition OFF, and still have UN-LOCKED POWER STEERING, and POWER BRAKES, as the car slows from engine compression, certainly seems like the way to go! This would give enough time to safely pull off the road and stop.

As long as the crank is turning, whether it’s done by combustion or by the inertia of the moving vehicle, you’ll have vacuum on the brake booster diaphragm and the power steering pump will be pressurizing the system.

However…much of the advice given was directed at all drivers of all vehicles. I’ve never checked, but I would not be surprized if on old vehicles with manual trannys the key could be turned “off” and lock the steering with the tranny in gear.

I still maintain that the best policy is to shift to neutral, get safely stopped, and THEN worry about the engine.

I had this same thought, but I drive a stick shift. If the accelerator stuck and you turned off the engine, but left it in gear and the clutch engaged you wouldn’t lose any power accessories. I hadn’t considered how this would work on an automatic, as I wasn’t sure the torque converter would transfer enough power to keep the engine rotating… It evidently does. How interesting. On another note my truck has a button that must be pressed in order to turn the key far enough to lock the steering column, so this would be unlikely to happen. it’s good to know there is some margin of error built into the power train.

Well, my old 68 Roadrunner never had power steering or power brakes to begin with and it wasn’t a difficult car to drive.


I think the reason the power steering was still active, and the engine ran when the ignition was clicked back on (I’m assuming without having to turn it to start), is that the transmission was turning the engine. If he would have slowed down much more, probably to the point where the transmission would have naturally downshifted, he would likely have felt the transmission ‘disengage’ and the engine would have stopped as the car continued to coast on. This works—I’ve tried it on several cars over the years.

In the old days, before fuel injection, this was a good way to make your car backfire violently and possibly blow a hole in your muffler.

What about airbags? Do they require the ignition to be on?

If you want them to deploy when you hit something, then yes. (They would probably work up to a second or two after you turned the key off, but no longer than that.)