You can use a multimeter to test the resistance to be sure. Q: How Can You Tell if a Spark Plug Is Firing? A: The grounding test is performed to determine if a plug is firing.

Spark Plug Wire Puller (For older vehicles without coil packs) Multimeter (for resistance test) Spark Plug Socket Sockets (for cars with coil packs) A spark plug that’s known to work ...

If replacing plugs doesn't solve the problem, check the spark plug wires, as they may be arcing to each other or electrical ground. Here's a trick: in a dark place, open the hood with the engine ...