If you drive a vehicle with a gasoline engine, thank the spark plugs for igniting the gasoline/air mixture in each cylinder that keeps your vehicle traveling smoothly down the road every day. Your spark plugs work hard, firing thousands of times in a well-choreographed order, and you usually don't pay much attention to them until one of them stops working the way it should.
Signs that spark plugs are wearing out include:
- Engine runs more roughly than it did
- Vehicle doesn't start as easily as it used to
- Vehicle hesitates when you press on the accelerator
- Your fuel economy has gotten worse
When a spark plug stops working altogether, you will find your engine has likely lost a lot of its power and isn't running smoothly. Your Check Engine light may come on. Then it's time to head to your service center to have it diagnosed.
If your plugs need to be replaced, they're usually done all at the same time. And if your vehicle has spark plug wires, experts recommend you change them as well. Different type of spark plugs last longer than others, and your service advisor can discuss what's best for your vehicle and driving habits.
A technician will also determine if there are any carbon deposits on your plugs, how healthy the ignition coil is (it's the part that supplies the high-voltage jolt that makes the spark) and will look for other signs and symptoms that may point to other problems in your engine. For instance, if a spark plug is fouled by oily deposits, it's possible oil is getting into the combustion chamber.
They will also check all the plugs to see if there are problems in just one or all cylinders. Sometimes a technician will find a plug that has overheated, literally melting the metal. In that case, they may recommend they correct that problem before replacing the spark plugs.
Most spark plugs will last for a good, long time. Even if you aren't seeing any symptoms they're wearing out, make sure you have your service advisor check your vehicle manufacturer's recommended maintenance intervals. Preventative maintenance will keep your vehicle running reliably, so you can count on it to get you where you want to go.