When the combustion process starts, the coil pack or ignition coil produces very high energy that reaches 75,000 Volts. Then, the ignition control receives a signal from the car's computer which releases the voltage from the coil pack that goes through the spark plug.
When the current travels to the spark plug, the spark plug fires an explosion inside the cylinder chamber due to the fuel-air mixture.
An ignition coil is an induction coil in an automobile's ignition system that transforms 12 volts to the thousands of volts needed to create an electric spark at the spark plugs.
A coil pack is a collection of ignition coils that eliminates the expensive and troublesome distributor, cap, and spark plug wires.
Coil packs provide better engine performance than distributors used in older vehicles. Some early coil packs were prone to frequent failure. But the modern ones can potentially deliver a better spark with less produced electrical noise. It is also worth mentioning that coil packs have a much longer lifetime than distributors.
Experiencing repeated misfiring and backfiring
Problem starting up the engine
Check engine light
A noticeable lack of power
Lower fuel economy
The first you should do if you expect problems with your ignition coil is read the trouble codes.
To do this you will need an OBD2 scanner.
Codes that are related to bad ignition coil are:
P0354 Ignition Coil D Primary/Secondary Circuit
P0351 OBD-II Trouble Code: Ignition Coil "A" Primary/Secondary
P0352 OBD-II Trouble Code: Ignition Coil B Primary/Secondary Circuit
P2311 OBD-II Trouble Code: Ignition Coil D Secondary Circuit
You may also notice P0300, P0301, P0302, P0303, P0304, P0305, P0306 cylinder misfire codes yet.
Don't worry about these codes. Replace the defective ignition coil, erase all codes with the OBD2 code reader and see if these codes come back.
It shouldn't be a hard task to test your ignition coil, all you need is an ohmmeter to test the coils primary and secondary resistance and compare its current readings with the standard readings in your vehicle's manual or by searching for the optimal readings on the internet.
You can buy an adapter that can be attached to the coil observe and scan secondary ignition data for each coil. It costs less than $50 each.
The main reason for ignition coils failure is worn spark plugs, excessive spark plug gap, or plugs wires. Heat can also affect the windings and insulation of the coil. The ignition coil increases the primary voltage from 12 Volts up to 40 thousands of Volts to fire the spark plugs. If there's an open plug wire or excessive resistance, the output voltage can burn the internal insulation of the coil.
Another reason for ignition coil failure is oil or coolant leaks which might damage the ignition coils.