How to tell ignition coil is good or bad?
Hi there - basic testing of ignition coils can be done with a volt meter, checking for shorts or a specified level of resistance (measured in ohms) in the coil windings. Failing coils require an oscilloscope (or similar testing tool) to observe the spark impulse coming out of the coil, looking for correct and consistent wave form, especially under load - such as when you "punch" the throttle. This is high-voltage work, and requires training and specialized equipment to avoid injury or worse. For assistance, I recommend an engine misfire inspection performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, and give you an accurate assessment of damage and cost estimate for repairs.