DRIVEABILITY/EGR SURGE OR HARD 3-2 DOWNSHIFT

DRIVEABILITY - EGR SURGE AND ABRUPT 3-2 DOWNSHIFT

Models Affected: 1988 2.OL OVERHEAD CAM L-4 ENGINE --------------- (VIN CODE M) IN SUNBIRD AND GRAND AM MODELS WITH AUTOMATIC TRANSMISSION

Some early built 1988 Sunbird and Grand Am vehicles with the L-4 turbo engine may demonstrate one or both of the following driveability conditions:

1. Exhaust Gas Recirculation (EGR) Induced Surge ----------------------------------------------

Light surge at road load driving conditions (approximately 40 mph) with a warmed-up engine. Disconnecting the EGR valve and plugging off the vacuum line will verify EGR induced surge.

2. Abrupt 3-2 Downshift --------------------

During a passing maneuver in the 40-55 mph speed range, a potentially harsh 3-2 downshift prior to normal torque converter clutch (TCC) unlock may occur. Other automatic transmission conditions (if present) should be corrected prior to any final verification of the above condition.

These conditions can be repaired by changing the ECM calibration PROM. Using a TECH 1 scanner, the original ECM part numbers can be verified.

PART NUMBER PROM ASSEMBLY Vehicles Built With ECM P/N 1608"4262"

16120036 PONTIAC J AND N

Use applicable Labor Time and Operation Number.

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.