---------- Some owners of 1990 and 1991 S trucks with 2.5L engines (VIN Code E) may comment of an engine detonation or idle roughness when cold or after a hot restart.
------ The Production calibration has a temporary lean condition when the engine is cold or after a hot restart.
----------- New MEMCALS have been released which address this temporary lean condition. Install the correct MEMCAL from the chart below:
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.