Which statement about spark plug wires is true?

The assertion that spark plug wires should be replaced if the resistance exceeds specifications is accurate because excessive resistance can lead to poor engine performance. Spark plug wires, also known as ignition leads, are crucial for transferring high voltage from the ignition coil to the spark plugs. If the resistance within a wire is too high, it can prevent sufficient voltage from reaching the spark plug, leading to misfiring, rough idling, and decreased fuel efficiency. Thus, monitoring the resistance of the wires is essential to ensure optimal engine performance, and replacing them when they exceed the manufacturer's specifications is a standard practice to maintain vehicle reliability.

The other statements do not encapsulate best practices. For instance, while cleaning spark plug wires can occasionally remove surface contaminants, it does not address underlying deterioration that may occur over time, making replacement more reliable. The idea of reusing cables indefinitely underestimates the wear and tear that can occur, resulting in compromised performance. Lastly, the notion that cables must be replaced in pairs is not always necessary; individual cables may wear out at different rates based on various factors. Therefore, the focus should be on the condition and performance of each wire rather than a blanket replacement policy.