Before beginning any diagnosis and testing procedures, visually inspect the components of the ignition system and check for a possible discharged battery, damaged or loose electrical connections, blown fuses or damaged vacuum hoses. Also inspect the rotor and distributor cap for excessive wear, the spark plugs for damage and make sure that the distributor cap, rotor and spark plug wires are properly seated. Check the spark plug wires and boots for signs of poor insulation that could cause cross firing. Turn all accessories off during diagnosis and testing. Make sure the idle speed is within specification.