INFO. ON EXHAUST SYSTEM 'RATTLE' MAY BE MISDIAGNOSED. Pontiac Sunfire 1997

SUBJECT: INFORMATION ON EXHAUST SYSTEM "RATTLE" MAY BE MISDIAGNOSED AS CATALYTIC CONVERTER RATTLE

MODELS: 1997 CHEVROLET CAVALIER 1997 PONTIAC SUNFIRE WITH 2.2L ENGINE (VIN 4--RPO LN2)

A METALLIC NOISE OR "RATTLE" MAY BE HEARD COMING FROM THE EXHAUST SYSTEM IN THE VICINITY OF THE CATALYTIC CONVERTER WITH THE ENGINE IDLING WHILE AT OPERATING TEMPERATURE. THE NOISE MAY BE MORE NOTICEABLE OUTSIDE THE VEHICLE OR WITH THE VEHICLE RUNNING NEAR AN OBJECT THAT REFLECTS SOUND.

A LOW MILEAGE ENGINE MAY INTERACT WITH THE EXHAUST SYSTEM CAUSING A RATTLE CONDITION. THIS CONDITION MAY BE MISDIAGNOSED AS A CATALYTIC CONVERTER RATTLE CAUSED BY A LOOSE MONOLITH OR PARTICLES INSIDE THE CATALYTIC CONVERTER.

THIS CONDITION IS CAUSED BY RESONANT ENGINE VIBRATION THAT EXISTS ONLY DURING ENGINE BREAK-IN. THE NOISE WILL TYPICALLY GO AWAY AFTER INITIAL ENGINE BREAK-IN, APPROXIMATELY 250 MILES (400 KM) OF DRIVING. DO NOT ATTEMPT TO REPAIR THIS CONDITION BY REPLACING EXHAUST SYSTEM COMPONENTS. IF THE CONDITION THAT IS NOTED DOES NOT GO AWAY AFTER APPROXIMATELY 250 MILES (400 KM) OF DRIVING, FURTHER DIAGNOSIS SHOULD BE PERFORMED TO CORRECT THE CONDITION.

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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.