It depends on the car. Older vehicles, with carburators and mechanical fuel pumps can continue to run after the engnine is turned off. It's a condition called "Piston Glow" or "run-on". If it's a newer vehicle, the fuel pump and injectors shut off immediately when you turn off the key so it's not possible to continute running unless there is a problem with the switch.
Timing set too far advanced and very low octane fuel may also cause dieseling (run- on). Before fuel injection this was common and some carburators had an electrical shut-off valve to stop the run-on.
It sounds like your dizzy cap isn't lined right which causes the engine to stay running after the ignition has been switched off. i had the same problem with my fiesta
Mine is doing the same thing, keep having to pull fuse to stop it
Timing issue - either cam or ignition.
Moe information is required to answer this question. Do yu mean why/how is the AC Blower still running?If this is the question it is probably because when turning the ignition switch off a delay timer leaves accessory power on for about 30 seconds before shutting down.
Not running on all cylinders? Bad spark plug or wire? Bad ignition coil (if C.O.P.)? Bad valve? etc.?
A bad connection inside the ignition switch will keep it from turning the engine over.
Lack of info Hesitation causes: Fuel filter, injector/s dirty, ignition problems are places to start
It could be the electrical ignition system. there is a recall, dealers will replace the ignition relay free of charge. check it out. Pontiac tele. #1-800-620-7668
I believe this usually this happens if the fuel / air mixture is not rich enough (too much air / too little fuel) which causes the cylinder heads to get too hot which means that any unburnt fuel in the cylinders will continue to ignite even after the ignition has been cut.
Detonation of the fuel caused by timing to high and/or low octane fuel. Have someone check the timing and use a higher octane fuel maybe a booster.
Head lights on?
You are more than likely hearing the electric fuel pump running. If it is noisy then it will fail in short order.