FORD

A: Ignition coils typically last upwards of 100,000 miles. Actual mileage will vary based on your vehicle and driving habits, but regular maintenance of ignition system components can help maximize the life of your coils.

A: Your engine sounds unhealthy.
You're no longer idling smoothly.
Your car suddenly stalls.
Your car starts backfiring.
Your check engine light comes on.

A: You don't always have to replace ignition coils with spark plugs, but it's often a good idea to do so if the spark plugs are difficult to access, as a failing spark plug can damage a coil, or if you want to prevent future issues. Spark plugs are routine maintenance items that wear out with normal use, while ignition coils are typically only replaced when they fail and cause a misfire.

A: After replacing an ignition coil, you should start the engine and take a short test drive to check for smooth operation and proper acceleration. If the engine runs rough, shakes, or the Check Engine Light (CEL) remains on or flashes, immediately shut off the engine and re-check your work to ensure the new coil and its connector are seated correctly and wires are secure.

A: Coil problems can cause loud backfiring from the exhaust system. Backfiring happens when the unused fuel that is pushed into the exhaust meets hot components and combusts. The combustion creates a loud, popping sound like a firecracker coming from the tailpipe.

A: To test an ignition coil, you can perform an on-vehicle "power balance" test by disconnecting each coil one by one to see if the engine's RPMs drop and it runs rougher, indicating a healthy coil, or a visual spark test using an inline spark or coil tester connected to the engine's ground to look for a strong spark, or a multimeter resistance test comparing the primary and secondary winding resistance against vehicle-specific service manual specifications.