Spark Plugs – The Good, the Bad, and the Buildup

The spark plug uses the energy produced by the ignition coil to generate the spark necessary to ignite the air/fuel mixture in the combustion chamber.

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Inspecting Your Vehicle's Spark Plugs

Normal wear and tear: the firing end should be gray or a brownish tan in color and relatively clean, indicating a normal running engine.

Ash deposits: Too much oil in the combustion chamber or low quality oil/fuel can cause light brown deposits to form around the electrodes and insulator. This development leads to misfiring and hesitation.

Carbon Fouling: Resulting from an over saturated fuel/air mixture, a clogged air filter, or a malfunctioning choke operation, dry black residue on the plug can cause misfire and a weak spark.

Oil Fouling: Resulting from either valve guides (in 4-stroke engines), too much lubricant (in 2-stroke engines), or oil leaking beyond the piston rings, wet oily residue forming on the plug can cause misfire and a weak spark.

Overheating: A malfunction in the ignition or cooling systems or using the wrong type of fuel can cause blistering along the white insulator and glazed electrodes.

Worn Out: Electrodes subject to significant wear and tear will have trouble starting in cold or moist conditions.


How Do I Replace My Spark Plugs?

Learn how to replace your vehicle's spark plugs with RepairPal Bret in the video below.

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