sounds to me like the ignition switch to test take the cover off that covers the switch flow the wires from the switch and you will find a plug unplug it the lights should go out if this happens put the plug back together start car then unplug the plug if the car stops its the switch just buy a new one and fit
SoundS like good advice to me ! For there to be power to the coil when you switch off you must have contacts fused together !
