Signs & Symptoms of Bad Spark Plug Wires

by Jason Medina

Spark plug wires are a critical link in a vehicle's electrical system. Responsible for transporting electrical power from a vehicle's ignition system to its engine spark plugs, spark plug wires need to function properly to ensure normal engine operation. When spark plugs wires fail, a host of engine problems can result.

Rough Engine Idle

The most common symptom of bad spark plug wires is a rough engine idle. Spark plug wires are responsible for transmitting the electrical current from a vehicle's electrical system to the engine spark plugs, where the electrical current is used to ignite the engine air/fuel mixture. Bad spark plugs wires can inhibit the normal flow of electrical current that reaches a vehicle's spark plugs, which can cause a rough, erratic engine idle.

Engine Miss

An engine miss, which normally occurs as the result of erratic or incomplete engine combustion, is another common symptom of bad spark plug wires. Many times, bad spark plug wires cause the flow of electrical current to the engine spark plugs to become erratic, alternating between brief periods of normal flow and brief periods of abnormal, erratic flow. The result of this is periods of erratic and incomplete engine combustion, which can manifest itself as an engine miss.

Engine Hesitation

Engine hesitation, which is normally most apparent during acceleration, is a condition that often results from either abnormal fuel flow to an engine or abnormal electrical conduction to a vehicle's spark plugs. Bad spark plug wires, whether they degrade internally or develop cracks and breaks in their outer coverings that cause electrical interference, can cause an engine to hesitate if they disrupt the normal flow of electrical current traveling from a car's battery to the engine spark plugs.

Reduced Engine Power

Proper electrical conduction to a vehicle's spark plugs is needed to ensure proper engine combustion and engine power. Any abnormalities in a vehicle's electrical system, including in its spark plugs and spark plug wires, can negatively affect spark plug firing, which will influence engine combustion and engine power. Bad spark plug wires can result in significant engine power loss if they inhibit or interfere with the normal flow of electricity that reaches a vehicle's spark plugs.

Engine Surging

A common symptom of a vehicle electrical problem is engine surging, a condition that happens when a vehicle experiences brief spurts of adequate electrical flow to its spark plugs, interspersed with brief periods in which electrical flow is reduced or nonexistent. Engine surging is a common symptom of bad spark plug wires, especially if the wires have cracks or breaks in their outside insulation, a condition that can create significant electrical resistance and lead to abnormal or completely stopped electrical flow to a vehicle's spark plugs.

About the Author

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