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25% Off Online Orders Over $100
Use promotional code FALL25 at checkout to receive discount. Not valid on tires, wheels, gift cards, special orders, installation, commercial or fleet purchases. Excluding the following brands; Edelbrock, Holley, Autometer, Accel, K&N, MSD, and BBk Performance. Not valid in combination with any other discounts or promotions. Valid online until 2:59 am EST on 11/28/14. Online orders scheduled for in-store pick ups must be completed in store by closing on 11/27/14 for discount to apply.

Free Shipping orders over $75
Free Ground Shipping on Ship to Address orders over $75. 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 from all shipping promotions and may require additional shipping fees. Please see item descriptions or visit our Shipping Policy page 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.