Ignition cables, also known as “spark plug leads” are part of the ignition system. They transfer the spark from the distributor or ignition coil to the spark plugs to ignite the air-fuel mixture which then starts the engine. Over time, the cables can weaken and break down. This will make it harder for the spark to reach the engine cylinders, resulting in engine misfires. A conventional plug wire has a resistance of 10,000 to 15,000 ohms per foot of length, if it's measurably higher, the lead is probably failing. A completely failed lead will have a hairline break and the resistance will be infinite. Replace ignition leads one at a time to maintain the exact routing configuration as the original and use silicone grease on the boots to allow easy removal for future replacement.
