It is called pre-ignition, find a friendly mechanic.
engine idle set too high or the timing is off and needs reset.
radiator fans running to cool engine...
Maybe your ignition switch has gone bad and you didn't rally turn off the eengine.
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
I'm not a gambling man but I would risk a shilling that the radiator fan is running Peugeot fans are not ignition controlled, and do start at times after the engine is switched off.
Not really enough information given - however - if they are badly out of adjustment you might be referring to the sound of the valves tapping - OR - you are hearing the noise of pre-ignition - perhaps the timing of the engine is off badly.
There could be several reasons why your Hyundai Atos engine is still running even though you have switched the ignition off. It could be a wiring problem in the engine. You will need to take the vehicle to a licensed mechanic.
if this is turbo you could have to much oil in and it gets into the turbo and will run on its own
check for a bad earth strap going t gearbox to battery
the diesel engine. it takes one ignition to start, then it runs off of (autoignition) ignition from heat caused by high compression. compression ignition (autoignition) causes ignition to happen a little earlier than spark ignition engines (gas engines) which is less vulnerable to risk of engine knocking or wasted power when dealing with high compression. -maddmatt
What Do You Think It Does? It Shuts Off The Ignition Of Your Engine, So Basically It Cuts The Engine Off...