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Re: Engine keeps running, ignition switch off?

> - a transmission failure kept the car locked in overdrive

> > Unlikely, but possible, I suppose.. > > > - the engine control computer kept the speed at about 70mph > > This is NOT possible. Unless the throttle cable was jammed, there is no way > the engine control system can keep the engine power up that high without the > gas pedal being down, because there is not enough air that can enter the > engine.

For *some* cars this is actually possible, althought not likely in this case.

Later Audi diesels have "fly-by-wire" gas pedals. The pedal is only connected to potentiometer telling the PCM how far down it is. The injection pump is electronically controlled, and the cruise control appears to be built into the PCM.

I believe some later BMW:s also have electronically adjusted valve trains instead of a throttle.

Thomas

Reply to
Thomas Tornblom
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A fair number of cars how have electronic throttle control, though the Sunfire is not one of them. Even then, such a failure would be exceedingly unlikely, since there are multiple redundant accelerator position sensors with such systems, and the throttle actuator is designed to go back to idle in the event that the mechanism fails. (On many systems, if a failure is detected in any part of the system, the engine power will be limited, down to idle in some cases, to prevent the possibility of out-of-control acceleration.)

Reply to
Robert Hancock

"Robert Hancock" wrote in news:RfR_b.594629$JQ1.228378@pd7tw1no:

OK, so the Sunfire doesn't have electronic throttle control. What part of the engine management system could possibly control the throttle? (I mean, aside from Cruise Control, which we are assuming she didn't have engaged.)

We are looking for a plausible mechanism to keep an engine revved up to take her on her 70mph runaway ride.

Reply to
Jim Land

There's nothing in that system that should be able to increase engine power to that level. The idle air control actuator can't allow that amount of airflow into the engine even if for some reason it was fully extended.

I'd guess some mechanical problem may have jammed the throttle open - or quite likely something sillier, such as a floor mat jammed on top of the gas pedal, or the driver pressing the gas instead of the brake or something..

Reply to
Robert Hancock

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