EXHAUST SYSTEM RESTRICTED DIAGNOSIS

OCCASIONALLY, AN OWNER MAY COMMENT OF POOR ENGINE PERFORMANCE OR LACK OF POWER WHEN THE IGNITION AND FUEL SYSTEMS ARE FUNCTIONING NORMALLY. THIS COULD BE CAUSED BY A RESTRICTION IN THE EXHAUST SYSTEM SUCH AS A BENT TAIL PIPE, RESTRICTED CATALYTIC CONVERTER OR OTHER CONDITIONS WHICH CANNOT BE DETECTED BY A VISUAL INSPECTION. A SIMPLE METHOD TO DETERMINE IF THE EXHAUST SYSTEM IS RESTRICTED IS THROUGH THE USE OF A VACUUM GAGE. WITH THE ENGINE AT OPERATING TEMPERATURE, CONNECT THE VACUUM GAGE TO ANY CONVENIENT VACUUM PORT ON THE INTAKE MANIFOLD. RUN THE ENGINE AT 1000 RPM AND RECORD THE VACUUM READING. INCREASE RPM SLOWLY TO 2500. OBSERVE THE VACUUM GAGE WHILE HOLDING THE THROTTLE STEADY AT 2500 RPM. IF VACUUM HAS DROPPED, THE EXHAUST SYSTEM SHOULD BE INSPECTED FOR RESTRICTIONS.

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.