TUNE-UPS: Now let's spend some time summarizing each system's maintenance procedures and outline some common problem areas, as well as giving you some additional information that you should know in order to clarify any questions you may have. The most important maintenance procedure for your ignition system is, of course, the ignition tune-up. A tune-up consists of replacing the distributor cap, if worn, the distributor rotor and the spark plugs. Make sure before replacing the spark plugs that you gap each one properly. Also, never allow dirt in the cylinder holes and insert spark plugs first by hand to avoid stripping them. Adjusting the ignition timing is rarely required on late model cars but is necessary on Pre-1975 vehicles. I recommend you tune-up vehicles with electronic ignition every 20,000 miles while for vehicles with points and condenser I recommend every 10,000 miles. Most late model vehicles utilize an electronic control unit which makes use of sensors to monitor both the air entering and the exhaust emissions exiting the cylinders as well as monitors the cooling system temperature and ambient air temperature. Using all this information the control unit meters and adjusts the fuel entering the cylinders so that it will burn most efficiently. Fuses and any fusible links act as safety overload mechanisms in the event of an electrical surge or short. Relay switches control the amount of electricity reaching a particular system or part while a ballast resistor reduces battery voltage for use in the ignition system.
