Inspecting Your Spark Plug Wires
*EASY*
You should visually inspect your spark plug wires monthly. Faulty wires will reduce engine performance and increase pollution. One misfiring plug can decrease gasoline mileage by up to 2 mpg. It is therefore important to make sure the wires are in good condition.
Check your spark plug wires as follows:
- Park the vehicle on level ground with the engine OFF, the parking brake engaged, and the transmission in PARK (for automatic) or REVERSE (for manual). If the engine has been run recently, let it cool. Raise the hood.
- Wrap a wire around your finger to flex the wire's silicone insulation.
Look for cuts, tears, cracks, kinks or other defects in the wire and boot.
A cut wire will not transmit full voltage to the spark plug; the fuel will not be completely burned. Do not attempt to repair any cut with tape. Spark plugs wires contain extremely high voltage current and must be kept clean, dry and perfectly insulated. Replace any damaged spark plug wire. (However, since spark plug wires are sold in sets, all plug wires are generally changed at the same time.) - Make sure the wire boot is firmly attached to the spark plug terminal. Do not permit oil to leak onto any spark plug wire. Do not let any spark plug wire touch a hot surface such as the exhaust manifold or engine block. Heat will damage the wire insulation.
- Check the routing of the spark plug wires. Do not permit spark plug wires
to touch each other or set too close together in a parallel direction.
Because of the extremely high voltages being conducted (about 25,000-40,000 volts), it is easy for one wire to induce voltage in another and cause misfiring. - Repeat the above three steps for each spark plug wire. Close the hood.
