Recommended intervals also require checking the spark plug wires as well as whenever new spark plugs are fitted in the engine. The first step is a visual inspection of the spark plug wires, which should be done when the engine is running in a dim garage with a good amount of ventilation. Turn on the starter and pay attention to every plug wire, making sure that you are not touching any parts of the engine that are in motion; a small spark or arc at a broken wire symbolizes a break. The engine is turned off, and the plug wire that is connected to one of the spark plugs is detached by holding the rubber boot, twisting it down a bit then pulling the wire off but not the wire itself. Look inside the boot, in place of corrosion would be white crusty powder, and be sure that the wire and boot are firmly in place on the spark plug, otherwise, with pliers, crimp the metal connector therein. Clean the wire length with a clean rag to get all the dirt and grease off, and see how many holes there are, areas burnt, any cracks and other damage, but do not over bend it. The wire connects the coil pack to the wire; pull it off with a boot pulling tool, if needed, and examine it to make sure that it is free of corrosion and fits the contact. Test the rest of the spark plug wires individually to make sure that they are firmly clamped on at each end. In case the new spark plug wires are required, then buy a set according to the engine model, but they have to be pre-cut and the rubber boots are already attached. Swap the wires sequentially so you do not confuse the firing order, mark the routing of each wire before disconnection and compare the old wires with the new wires to make appropriate replacements.