POOR ENGINE PERFORMANCE PLUGGED DUAL BED CATALYTIC CON

PROPER DIAGNOSIS OF A PLUGGED CATALYTIC CONVERTER IS ESSENTIAL BEFORE THE CONVERTER IS REPLACED IN SERVICE. THE FOLLOWING DIAGNOSTIC PROCEDURE IS RECOMMENDED: 1. REMOVE HOSE AT LEFT OR RIGHT (WHICHEVER IS EASIEST) MANIFOLD A.I.R. CHECK VALVE, THEN REMOVE CHECK VALVE. 2. USING HOSE AND NIPPLE (FIGURE 1) FROM THE PROPANE ENRICHMENT DEVICE (J26911), CONNECT HOSE TO A FUEL PUMP PRESSURE GAUGE. 3. INSTALL NIPPLE INTO THE MANIFOLD AIR PIPE. 4. WITH ENGINE AT NORMAL OPERATING TEMPERATURE, RUN THE ENGINE AT 2500 RPM AND OBSERVE BACKPRESSURE READING ON GAUGE. 5. IF BACKPRESSURE MEASURES 2 3/4 PSI OR GREATER, A PLUGGED EXHAUST SYSTEM IS INDICATED. 6. INSPECT MUFFLER FOR HEAT DISTRESS OR POSSIBLE INTERNAL FAILURE. 7. IF NO OTHER CAUSE FOR EXCESSIVE BACKPRESSURE IS FOUND, REPLACE THE CATALYTIC CONVERTER OR WITH OEM CONVERTER OR AS OTHERWISE DIRECTED IN SERVICE BULLETINS. NOTICE: IT IS VERY UNUSUAL FOR SINGLE BED BEAD CONVERTERS TO PLUG WITHOUT OBVIOUS SIGNS OF EXPANSION OR HEAT DISTRESS (EXCEPT IN CASES WHERE LEADED GASOLINE IS USED).

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.