A spark plug detonates the mixture of air and gas in the cylinder of an internal combustion engine, causing an explosion that moves the piston and turns the crankshaft. In 2003, the Chevrolet Impala came equipped with a 3.4-liter V-6 in the base model or a 3.8-liter V-6 in the LS and higher versions. For maximum performance and fuel efficiency and a smooth-running engine, Chevrolet recommends changing the spark plugs every 100,000 miles.
Allow the Impala to sit until the engine is cool. While the engine is cooling, assemble your tools and locate the spark plugs by following the wires onto the engine block. The front three are easy to see, but the three on the rear bank of cylinders are concealed by the intake manifold. You will have to trace the spark plug wires on those with your hands.
Disconnect the negative battery cable. Raise and support the front end of the vehicle. Due to the placement of the plugs on the rear bank of cylinders, it will be easier to remove and install them from underneath the vehicle or through the side. Squirt a non-silicone penetrating lubricant into each spark plug well to aid in the removal of the plugs.
Remove the wire from the first spark plug. Fit the spark plug socket onto the extension bar and attach the bar to the ratchet wrench. Fit the socket over the spark plug and wiggle it until it seats. Gently turn the handle of the wrench counterclockwise. Remove and discard the plug once you unscrew it.
Coat the threads of the new plug with anti-seize compound. Apply a small amount of dielectric grease over the electrode. Guide the new plug into place using the extension and socket. Carefully hand-tighten the plug until it will not turn any more. Fit the ratchet onto the extension and tighten it slightly. Press the spark plug wire onto the electrode until it clicks. Repeat Steps 3 and 4 for the other two plugs on the front bank of cylinders.
Slide under the Impala and remove the spark plug wire from the right-most plug. Fit the socket onto the extension and use the extension to guide the socket onto the plug. Fit the end of the ratchet onto the extension and turn it counterclockwise to remove the plug.
Coat the threads of the new plug with anti-seize compound and the electrode with dielectric grease. Guide the new plug into place using the extension and socket. Carefully hand-tighten the plug until it will not turn any more. Fit the ratchet onto the extension and tighten it slightly. Press the spark plug wire onto the electrode until it clicks. Repeat Steps 5 and 6 for the other two plugs on the rear bank of cylinders. Slide out from under the Impala. Reconnect the negative cable to the battery. Close the hood.
