INTERMITTENT HIGH IDLE ON SHIFT TO DRIVE. GMC Truck Jimmy

HIGH IDLE ON INITIAL SHIFT INTO DRIVE GEAR

VEHICLES AFFECTED: 1987 AND EARLY 1988 J-CAR 2.0L ----------------- (VIN CODE K),P-CAR 2.5L (VIN CODE R), AND S/T/M-TRUCK 2.5L(VIN CODE E) AND AUTOMATIC TRANSMISSIONS

Customer comments of a higher than normal engine idle RPM upon initial drive gear engagement that decreases within a few seconds, may be due to an ECM software condition. This drive only RPM condition is similar to a "carbureted fast idle" or "high cam step" level.

The above condition may be brought on by repeated engine "revving" in park/neutral or by a rolling/stopping action while in neutral. This condition will occur in a non-A/C vehicle or with A/C off in a vehicle equipped with A/C.

If this condition is experienced on a vehicle and the basic engine, engine controls and systems are performing properly and cannot be repaired using currently published Service And Diagnostic Procedures, it may be necessary to install a new ECM calibration PROM as follows:

PASSENGER __________________________________________________________ Fix M.Y./Div. Carline Engine (VIN) PROM

1987-88 Pontiac P 2.5L (R) 16122663

1987 Pontiac J 2.0L (K) 16086774

1988 Pontiac J 2.0L (K) 16086125

1987 Buick and Oldsmobile J 2.0L (K) 16086856

1988 Buick J 2.0L (K) 16086129

TRUCKS ____________________________________________________________

1987 Chevrolet and GMC S 2.5L (E) 16088437

1988 Chevrolet and GMC S 2.5L (E) 16088437

1987 Chevrolet and GMC T 2.5L (E) 16086793

1988 Chevrolet and GMC T 2.5L (E) 16086793

1987 Chevrolet and GMC M 2.5L (E) 16086797

1988 Chevrolet and GMC M 2.5L (E) 16086797

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.