An ignition coil transforms ignition voltage (12 volts) to the very high voltage pulses (20,000 volts or more) that fire the spark plugs. The number of ignition coils varies depending on car model and year of production. Older cars will have one coil covering all engine cylinders while newer cars may have a coil-on-plug type arrangement — that is every cylinder will have its own dedicated ignition coil.
The ignition is checked to assure it is in the “off” position. For single coils that supply all cylinders, the coil is disconnected from either a bracket located in the engine compartment or, in some cases, is removed from within the distributor. The replacement coil is secured and all electrical connections reattached. If the distributor was removed for any reason, the timing is adjusted as required. The coil is detached from the top of the individual spark plug for individual coil-on-plug applications and replaced. Once the coil is securely in place, all electrical connections are reattached, and timing adjusted as needed, the car is road tested to ensure normal operation.
Yes. A malfunctioning ignition coil will cause loss of power and lower fuel efficiency but that will not present an immediate safety issue. If the coil malfunction is causing misfiring, this will allow unburned fuel to enter and permanently damage the catalytic converter from overheating.