A: Make sure to check the Spark Plug wires either at the specified intervals or when new spark plugs are being installed. One wire at a time, disconnect it from the spark plug either by twisting and pulling on its rubber boot or using a removal tool. It is not advisable to pull out the whole wire. See if there is any white crusty powder inside the boot. Also, make sure that both of them are tight enough against the spark plug. In case they do not fit properly, use pliers to crimp the metal connector inside the boot. At this point, clean all dirt and grease from throughout the length of the wire with a piece of cloth before looking for burns, cracks or other forms of damage. This test is necessary to check if the wire inside is still conductive. The wires should be checked in exactly the same manner as spark plugs at distributor level. Put each wire securely back in place both at distributor and spark plug ends. In order to visually check whether there is any arcing or sparks indicating a break or fault, one can start his/her car engine in a very dark garage having ventilation facilities around him/her. When replacing them, get a new set that corresponds to your particular engine model and change wires one by one so as to maintain sequential firing order.