The main role of a spark plug is to produce an electric spark in the engine’s combustion chamber; therefore, when a spark plug is malfunctioning, the effects are often clearly shown by the engine response. This is a good indication that a spark plug needs to be changed.
The most common bad spark plug symptom is rough engine idle. When an engine is idling, it produces an ordinary smooth sound. However, if the engine sounds rough, and the vibration of the vehicle is greater than usual, a driver should inspect the plugs.
Another common symptom of faulty spark plugs is that the engine faces difficulty in starting. Apart from causes, such as running out of fuel or battery power, a faulty or worn spark plug can also cause the engine to have trouble starting. This is because it could not produce the spark needed to ignite the fuel and air mixture.
In addition, an engine misfire issue is also often rooted from a bad spark plug. Due to the faulty spark plug, the engine cylinder is not fired properly,leading to other symptoms, such as poor acceleration and higher fuel consumption. Furthermore, the engine may tend to start and stop suddenly, causing engine surging that can be dangerous when the vehicle is moving in heavy traffic.