The 2002 GMC maintenance schedule includes tuning it up every 30,000 miles or 3 years, whichever comes first. Because this vehicle is fuel injected, the tune up consists mostly of changing the spark plugs. Many people prefer to do an "extended" tune up, which includes changing the wires, distributor cap and rotor. Keeping the ignition system in tip-top shape ensures proper running and ultimate fuel economy.
Remove the plugs and wires from their boxes. Line the wires up on the front of the vehicle. If the type of plug you purchased has a ring, thread the ring over the threads of the plug. Mark the plugs and wires at the distributor cap. Match-mark the cap to the distributor base. Number the wire terminals with the same numbers as the spark plug wires. Hold the new cap up to the old cap, and mark it in the exact same places that you marked the old cap, including the match-mark.
Pull the plug wire off one of the plugs, using your fingers or the spark plug pliers. Remove the plug, using the spark plug socket. Insert the new plug and screw it into the head by hand as far as it will go. Tighten it firmly with the spark plug socket. Do not over-tighten the plug, as you will break the ceramic.
Follow the wire up to the distributor cap. Remove the wire from the distributor cap. Match the wire to one of the new wires to find the correct length. Push the wire onto the plug until it snaps into place. Push the other end of the wire onto the new distributor cap, ensuring that you put it on the proper terminal. Repeat Steps 2 and 3 for the rest of the plugs and wires.
Remove the distributor cap, using the appropriate socket. Remove the rotor, using the appropriate socket. Install the new rotor and tighten the retaining bolt firmly. Install the new cap by matching up the match-mark on the cap with the mark on the distributor body.
Check and top off the power steering fluid, brake fluid, coolant, engine oil and transmission oil. Check the belts for wear and replace as needed.
