SPARK PLUG FOULING HOT ENGINE DIESELING

SOME 1981 3.8 LITER ENGINES ARE ENCOUNTERING SPARK PLUG FOULING, POOR DRIVEABILITY AT LOW AMBIENT TEMPERATURES AND HOT ENGINE DIESELING. A NEW CALIBRATION (PROM) HAS BEEN RELEASED WHICH REDUCES AVAILABLE FUEL DURING THE OPEN LOOP PORTION OF CONTROL, RESULTING IN IMPROVED COLD DRIVEABILITY AND PERFORMANCE AND MINIMIZATION OF HOT ENGINE DIESELING. THE FOLLOWING PROCEDURE SHOULD BE USED TO CORRECT THE ABOVE STATED CONDITIONS. 1.REPLACE THE PRODUCTION PROM IN THE ECM WITH THE NEW PROM (SEE CHART BELOW). FOLLOW PROM REPLACEMENT PROCEDURE IN SERVICE MANUAL SUPPLEMENT #ST-329-81A PAGES 6E1-52 AND 6E1-53. VEHICLE TYPE A-COUPE, SEDAN AND SPECIAL W/AUTO TRANS PROM # 1225364 CODE 2168ABP VEHICLE TYPE A-WAGON, EL CAMINO AND F-CAR W/AUTO TRANS PROM # 1225363 CODE 0740ABS VEHICLE TYPE B-CAR W/AUTO TRANS PROM # 1225362 CODE 0763ABR VEHICLE TYPE ALL VEHICLES WITH MANUEL TRANS PROM # 1225360 CODE 076ABT 2.DISCONNECT ELECTRICAL CONNECTION OF EMR LEAD AT THE DISTRIBUTOR LEAD, AND TAPE TOGETHER AS SHOWN IN FIGURE 1. 3.THE FOLLOWING SHOULD ALSO BE CHECKED AT THIS TIME: A) SPARK PLUGS FOR CARBON FOULING AND LIQUID FUEL WETTING B) ENGINE OIL FOR FUEL CONTAMINATION AND PROPER LEVEL C) VACUUM BREAK ADJUSTMENT (SHOULD BE 25F) D) ENGINE TIMING AND FAST IDLE ADJUSTMENT PER VEHICLE EMISSION LABEL * ILLUSTRATION *

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.