Sluggish. Squealing. Unreliable. Vibrating. If any of these descriptors fit your vehicle’s recent behavior, it just might be trying to tell you something – like it’s time for a tune-up.

Today’s vehicles differ significantly from their decades-old brethren that required a tune-up every 10,000 or 20,000 miles. With newer vehicles, it’s increasingly common for manufacturer-recommended service intervals to stretch to 100,000 miles before certain maintenance items, such as replacing the spark plugs, should be completed. 

Spark plugs have been around since the beginning, and play as important a role now as they did a hundred years ago. It’s a good idea to replace them as a set at regular intervals, but sometimes one will go bad sooner than the rest for one reason or another. How do you know if you have a bad spark plug? Here are some indicators, from ACR Diesel & Auto Repair LLC in Kingman, AZ.