Spark plugs are one of those maintenance items ... Misfires, especially, will usually trigger a check engine light, but other symptoms of a bad plug are often undetectable by a vehicle's onboard ...

Spark plugs come in a variety of types, each with their own respective capabilities and lifespan, so it's important to know the difference when buying new ones.

The other telltale symptoms of bad diesel glow plugs include rough idling, misfiring, and lousy fuel economy, the same signs you'll notice when a spark plug goes haywire. Fortunately, glow plugs ...