Spark plugs are essential for your engine to start and run smoothly because they create the spark that ignites the fuel/air mixture in your cylinders. Plugs should be changed at the manufacturer’s recommended mileage (or as often as 30,000 miles or so if you’re following a preventative maintenance strategy). If you’re not sure when they were changed last and your engine is running rough or having trouble starting, bad spark plugs are a common culprit.
You can check your plugs by popping off the plug wires and using a socket wrench to remove them. The electrode — the end of the plug that is in the engine — should be brown or light gray. Black, wet, or deposit-covered electrodes are a common sign of a plug that’s no longer doing its job. Changing spark plugs is simple on most engines. It’s best to remove and replace one at a time so you don’t lose track of plug wire placement.