How Do I Know If My Ignition Coil Is Bad?

How Do I Know If My Ignition Coil Is Bad? Engine misfires. Rough idle. A decrease in car power, especially in acceleration. Poor fuel economy. Difficulty starting the engine. Check engine light is on. Exhaust backfiring. Increased hydrocarbon emissions. How do I know if my ignition coil or spark plug is bad? Illuminated Check Engine