POOR COLD DRIVEABILITY/4.1L NEW PROM AND THERMAC SENSOR

MODELS AFFECTED: ALL FEDERAL 1982 & 1983 REGALS AND REGAL WAGONS EQUIPPED WITH A 3-SPEED TRANSMISSION, CODE MX2, LESABRES EQUIPPED WITH A 4-SPEED TRANSMISSION, CODE 200-4R MXO, AND ELECTRAS

A new 4.1L/LC4 calibration has been released for production and service on the above models. This new driveability fix is to be used for dealer correction of any one of or combination of the conditions listed below, when it has been determined that affected systems are within specifications and are functioning normally.

The changes consist of the following:

1. New thermac sensor 2. New PROM

The following conditions describe when to use the changes:

1. Poor cold acceleration maneuvers 2. Tip-in stumble or sag during warm-up and excessive burst knock

Before a decision is made to install the new parts, the vehicle should be road tested, if possible, for the owner described conditions and vehicle systems checked to determine if adjustments are within specifications. Unless all areas listed on the checklist are correct, a parts change will not be effective for the purpose intended.

One part cannot be installed without the other.

Zone authorization is required prior to usage of the parts.

PARTS ORDERING INFORMATION

Thermac Sensor 8997916 PROM Regal 1226481 LeSabre & Electra 1226482

WARRANTY INFORMATION

Thermac sensor and PROM

Labor Operation T0119 Labor Time 0.7 Hr. Trouble Code 92

System performance check will not be required with this change.

BURST KNOCK (MOMENTARY DETONATION) CHECKLIST

Ignition Timing E.F.E. Operation EGR Valve System Operation T.A.C. Operation Vacuum Hoses and/or Connection Leaks Overheating-Cooling Sys. Prob. Carburetor for Lean Operation Incorrect Spark Plug Deposits in Combustion Chambers Bad Fuel Intake Valve Seals not Sealing E.S.C. not Working MAP/BARO Sensor Operation (If Equipped)

COLD DRIVEABILITY HESITATION, STUMBLE OR SAG CHECKLIST

Accelerator Pump System Operation (Pumpshot) Vacuum Breaks Choke Carburetor Float Level EGR Valve Operation Park-Neutral Back Up Light Switch Adjustment Thermac Air Cleaner (T.A.C.) Operation, Including Stove Pipe to Air Cleaner HEI Operation Evaporative Emission Control System (EECS) - Purge Solenoid Operation - Hoses and Hose Connections - Canister Vent Valve Operation Base Timing and Electronic Spark Timing (EST) Early Fuel Evaporation (EFE) System Mixture Control Solenoid Checks - Dimensionally Setting of Carburetor per the Procedure in the 1983 Buick Chassis Service Manual using Tools J-33815-1 and J-33815-2 - Spark Plug and Plug Wires

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.