Performing a tune-up on your vehicle's engine can help keep it in the best condition possible. Guidelines on how often a vehicle should be tuned usually rely on mileage, but what you use your vehicle for will also be a factor. If your GMC is used for heavy-duty applications such as towing or hauling, it may require more frequent tune-ups. You'll also need to perform more frequent tune-ups if you often travel muddy or dusty roads. Consult your GMC owner's manual for information on how often your specific vehicle should be tuned.
Turn off your engine and wait for it to completely cool.
Change the oil. Place an oil pan under the oil plug. Unscrew the plug and let all oil drain into the pan. Wipe the plug clean and replace it. Remove the oil filter. Apply a small amount of new oil to the gasket on the new oil filter. Screw in the new oil filter. Fill the oil reservoir with new oil. Check the oil dipstick for a proper oil level.
Remove the air filter cover and air filter. Replace the air filter and re-attach the cover.
Remove the spark plugs. Check for corrosion, dirt and oil. Scrub them with wire brush if needed. Use the gapping tool to check for proper gap. If replacement is neccessary, use the gapping tool to obtain the gap recommended in owner's manual before screwing in the new plugs.
Check the spark plug wires for corrosion, fraying or wear. If replacement is neccessary, remove and replace one wire at a time to ensure proper firing order.
Change the coolant. Placea a large container under the radiator. Empty the radiator into a container. Fill the radiator with pre-mixed coolant/antifreeze. Fill the coolant reserve tank to the proper level.
Remove the fuel filter and replace it with a new one. You may need to remove some engine accessories to get at the fuel filter.
Start the engine. Check the transmission fluid level on dipstick. Fluid should be pinkish colored. Add or replace as neccessary.
