"Dave Plowman (News)" wrote in message
...
Basically we're talking older cars. Many modern ones are drive by wire, so
far less likely the throttle can stick open.

I suppose any fault with the pedal position sensor that feeds info to the
ECU could cause the engine to race uncontrollably. However if you press the
brake, the ECU *may* be designed to cut the power on the basis that you
shouldn't be braking and accelerating at the same time - the ECU doesn't
know whether it's a stuck sensor or your foot hard on the throttle pedal.

A lot depends on where the sensor is. If it's in the footwell, right by the
pedal, it's less likely to stick. If it's at the far end of a bowden cable,
under the bonnet, as was the case on my first diesel car, then a frayed
cable *could* be a problem.

But, yes, I was talking about an older car with no ECU and a carburettor
which will carry on pumping fuel and air mixture as long as the cylinders
suck it in, and an engine that will carry on igniting the mixture until the
HT (or LT) is cut off.

My dad made a Heath Robinson immobiliser on one of his cars - I think it was
one of his Citroens. Since none of us smoke, he modified the cigarette
lighter with a steel disc that my grandpa turned on his lathe instead of the
normal heating element, and altered the wiring to put this "switch" in
series with the LT. Unless you pressed the cigarette lighter in, the car
would never fire. OK, so a savvy thief might hot-wire the coil directly to
the battery, but it would deter opportunistic thieves. He had to remember to
change the wiring back for when he sold the car :-)

That would have been a great kill switch in this situation: pull the
cigarette lighter out and the spark goes away, even though the key is still
in its original position and so there is power to everything except the
ignition. Not that he anticipated that need...