How Do I Know If My Spark Plugs Need to Be Replaced?

by Herb Gordon Subaru

Internal combustion engines need three basic elements to run—fuel, air, and spark. Air moves into the engine via the air intake, fuel is added to the cylinders through the fuel injectors, and spark is added by the spark plugs. To power your engine, the air/fuel mixture is compressed on the piston’s upward stroke. Once the piston reaches the top of its stroke, the spark plug conducts a spark that ignites the mixture, sending the piston on its downward stroke.

This cycle happens constantly as you drive, meaning your spark plugs fire hundreds of times per minute, just when your engine is idling and thousands of times per minute as you drive. That little spark is essential to your engine’s efficiency and power production. If the spark is weak, it may not burn all of the fuel in the cylinder, resulting in poor performance.

There is one spark plug per cylinder, so if you drive a vehicle with a four-cylinder engine, your engine has four spark plugs. Just one bad spark plug can cause problems, and if all of them go bad, your engine cannot run. Most auto manufacturers suggest replacement every 30,000 miles or so, but that depends heavily on the type of materials used to make your spark plug. The more durable the materials, the longer the spark plug will last.

Know your car and pay attention to some of these signs of worn-out spark plugs:

Rough or hesitant start-up
Bucking or chugging feeling when you accelerate
Reduced fuel economy
A check engine light
Exhaust that smells like unburned fuel
Rough idle

The Herb Gordon Subaru service department can help you determine if you need to replace your spark plugs, as well as any other components in your ignition system to keep your vehicle running smoothly, so contact us today. Remember, proper maintenance is preferable to waiting too long and having to do a much costlier replacement.