A: The Spark Plug wires should be checked at the recommended intervals or whenever new spark plugs are installed. To inspect the wires, remove one wire at a time from the spark plug being careful not to mix up their arrangement. Use a removal tool or twist and pull at the rubber boot to get rid of it. Look into the boot for corrosion which looks like white, crusty powder. Push back the wire and boot onto the spark plug making sure it is very tight. Pliers can be used to crimp metal connector inside the boot if necessary. Clean out any dirt and grease from wire using a rug and look for burns, cracks or other damages. Bend the wire in several places to check for its flexibility. Disconnecting it from distributor check for corrosion and make sure that it fits properly. On distributor reinstall boot or retaining ring. Repeat this procedure for remaining spark plug wires making sure that they are tightly held at both ends. Alternatively, do a visual check in a dark garage looking at each wire while arcing or sparking occurs on them. When replacement is needed, buy new ones labeled as per your engine model and change one wire at a time to avoid firing sequence mix-up.