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25% Off Online Orders Over $100
Use promotional code SECRET25 at checkout to receive discount Receive 25% off your total purchase of $100 or more of regularly priced in-stock single parts or accessories purchased online. Enter promo code SECRET25 in cart when purchased online to receive discount. Offer is not valid in combination with any other offers, rebates or discounts; not available to Pep Boys' Fleet & Commercial accounts; does not apply to labor, special order merchandise, tires or the purchase of gift cards. Valid online until 2:59 am EST on 5/4/14. Online orders scheduled for in-store pick up must be completed in store by closing on 5/3/14 for discount to apply.

Free Shipping orders over $75
Free Ground Shipping on Ship to Address orders over $75. No code needed. Offer only valid on in-stock merchandise valued at a total of $75, after any discounts have been applied, and before any core charges, shipping charges, fees and taxes have been added. Certain items exceeding weight and size limitations are excluded. See item descriptions for details.

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.