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25% Off Online Orders Over $50
Use promotional code PEPBOY2550 at checkout to receive discount. Receive 25% Off Online Orders Over $50. Not valid in combination with any other discounts or promotions. Not valid on gift cards, special orders, installed merchandise, commercial or fleet purchases. Excludes the following categories: Tires, Wheels, Brake Parts, Truck Boxes, Vent Visors, Bug Shields, Electronics and BRANDS: Razor, Traxxas, Superchips, Hypertech, Edge, Bully Dog, Diablo, Edelbrock, Holley, NOS, Proform, Specialty Auto, Autometer, Accel, K&N, Kenwood, Pioneer, Sony, Garmin, JVC, MSD and BBK Performance. Valid online until 2:59 am EST on 10/15/15. Online orders scheduled for in-store pick up must be completed in store by closing on 10/14/15 for discount to apply.

Haynes Tech Tips - Spark Plugs


Are your spark plugs trying to tell you something?

They can tell you a lot about the condition of your engine. If one or more of your spark plugs have sooty black deposits, that cylinder is probably using too much fuel or misfiring. Oily black deposits are often a sign that oil is getting into the cylinder, usually either past the piston rings or the valve guides.

There’s more spark-plug detective work you can do using the color spark plug chart that’s included in each Haynes model-specific repair manual.