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.

Image courtesy of Wikipedia

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.

0 User Comments

Sign in to comment
Why RepairPal?

Asset 71
High Quality Repairs
Your auto repair done right, only the work you need with no add ons.
Asset 72
Never Overpay
Our free estimator calculates a custom price for your vehicle repair.
Asset 73
Guaranteed Repairs
Rest easy knowing you're covered by our RepairPal Nationwide Warranty.