STALL, TIP-IN LAG OR ROUGH RUNNING ON COLD START

Subject: STALL, TIP-IN LAG OR ROUGH RUNNING ON COLD START, AMBIENT TEMP 50-80 DEGREES (DECARBON VALVES) Models Affected: 1988-90 GRAND AM AND GRAND PRIX MODELS W/2.3L

Some 1988-90 Grand Am models and 1990 Grand Prix models with 2.3L VIN codes A and D, may exhibit one or more of the following conditions for the first minute of cold, heavy throttle driveaway during ambient temperatures of 50-80 degrees Fahrenheit.

- Stall when put in gear

- Tip-in hesitation after immediately put in gear.

- Reduced cold engine driveability (miss, rough running or backfire).

If any of the above conditions cannot be repaired through proper service manual diagnosis, refer to Pontiac Service Bulletin 88-8-11 issued 3/88 for injector harness routing, refer to Pontiac Service Bulletin 89-6-27 issued 2/89 for 1988-89 Grand Am models for the latest mem-cal, inspect vacuum lines, especially the map sensor for kinks or restrictions, it may be necessary to inspect the intake valves.

To inspect the intake valves effectively, remove the intake manifold. If upon inspection the valves are found to have substantial deposit formation, it will be necessary to decarbon the intake valves using the Kent-Moore Carbon Blaster II, J 38375 along with adapter kit J 38743 to remove these deposits. Operating instructions are included with the tools.

Once deposits are removed, the owner of the vehicle should be advised to use fuels advertised to control deposit formation in engines.

A Carbon blaster and the necessary adaptor may be available through your zone office.

WARRANTY INFORMATION:

Labor Operation Number: T4674

Labor Time: Grand Prix 2.0 hours Grand Am 1.6 hours

Trouble Code: 92

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.