What Are the Symptoms of Incorrectly Gapped Spark Plugs?

by Jason Medina

Engine spark plugs are responsible for igniting an engine's air-fuel mixture, a process that creates engine power. Incorrectly gapped spark plugs can negatively impact engine performance. A list of some of the most common symptoms of incorrectly gapped spark plugs is laid out below.

Rough Engine Idle

An engine that has a rough, irregular engine idle is often due to spark plugs that are incorrectly gapped. Spark plugs that are gapped incorrectly upset the air/fuel mixture, which in turn affects engine combustion and idle.

Engine Hesitation

An engine that hesitates, or stumbles, upon acceleration is often the result of incorrectly gapped spark plugs. If spark plugs are gapped too wide, the ignition spark loses some of its strength as it crosses the spark plug gaps. This can result in engine hesitation.

Engine Missing

Spark plugs that are gapped incorrectly can cause an engine to miss, or run erratically, especially during idle. The incorrect spark plug gaps can cause uneven firing of individual spark plugs and delay engine combustion; both of which can cause an engine to miss or idle erratically.

Poor Engine Performance

For an engine to run at optimal levels, its spark plugs have to be gapped according to factory specifications. Any spark plugs that are gapped incorrectly can result in poor engine performance by altering engine combustion, weakening the ignition spark, and delaying the arcing of the ignition spark as it crosses each spark plug diode.

Engine Knocking

Engine knocking, or engine pinging, is a classic sign of an engine that has incorrectly gapped spark plugs. Engine knocking is the result of incomplete or delayed engine combustion, especially under acceleration.