During every tune-up/inspection, visually check the spark plug cables for fluid contamination, burns, chaffing, cuts, or breaks in the insulation. Check the boots and the nipples on the ignition coil or distributor, if equipped. Replace any damaged wiring.
Every 60,000 miles (96,000 km) or 48 months, the resistance of the wires should be checked with an ohmmeter. Wires with excessive resistance will cause misfiring, and may cause the engine to be difficult to start in damp weather. Ignition wire resistance should not be greater than 25 kilohms.
To check resistance, remove the spark plug wire from the plug and ignition coil or distributor. Using an ohmmeter, measure the resistance of the wire by placing one lead of the ohmmeter at one end of the ignition wire, and the other ohmmeter lead at the other end of the ignition wire.
If the measured resistance is above the specifications, the ignition wire must be replaced.