NEW DESIGN SPARK PLUGS LONGER CERAMIC INSULATOR

SUBJECT: NEW DESIGN SPARK PLUGS (SERVICE INFORMATION)

VEHICLES AFFECTED: 1991 TRUCKS AND CARS WITH CPC GAS ENGINES

For 1991, GM has introduced a new design spark plug for use in all cars and trucks equipped with CPC gasoline engines. These new design spark plugs have a ceramic insulator which is approximately 3mm (1/8") longer than the insulator used in previous model years.

When servicing these new design spark plugs make sure that spark plug socket being used is deep enough to accommodate the longer length insulator. Use of a spark plug socket which is not deep enough may result in the ceramic insulator becoming cracked above the spark plug shell. Cracking of the insulator may result in an arcing and intermittent engine misfire. This arcing may or may not be visible.

Check with the various tool manufacturers for deeper spark plug socket availability.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.