EXHAUST RATTLE/RINGING NOISE 3.4L V6 ENGINE (INFORMATIONAL)

SUBJECT: EXHAUST RATTLE/RINGING NOISE - REPLACE MUFFLER ASSEMBLIES AND EXHAUST INTERMEDIATE PIPE

MODEL/YEARS: 1991-92 CUTLASS SUPREME W/3.4L (VIN X) ENGINE

CONDITION: Some 1991-92 Cutlass Supremes with the 3.4L (VIN X) engine, may exhibit an audible metallic rattle/ringing type noise that appears to be coming from the rear underbody area of the vehicle, evident during vehicle warm-up after cold start.

CAUSE: Combination of the engine fuel/air ratio prior to reaching normal operating temperature and unequal length exhaust takedown pipes, generate exhaust pulses that create a resonance in the exhaust system.

CORRECTION: Replace existing exhaust intermediate pipe, right and left hand muffler assemblies with new components indicated below. Parts are currently available from GMSPO. To insure proper installation follow the procedure in the applicable Service Manual Section 6F, Exhaust System.

Description P/N ----------- --- Intermediate Pipe 12520500 L.H. Muffler Assembly 10220042 R.H. Muffler Assembly 12520505 Clamp 10114745

Note: Owners should be informed prior to servicing their vehicle, that the sporty/throaty exhaust note of the system will be appreciably reduced with installation of these new components. Knowing this, some owners may wish to forego the servicing of their vehicle for correction of the rattle/ringing noise apparent only during vehicle warm up.

Note: Insure that damper assemblies mounted on muffler crossover pipe are reinstalled if vehicle was equipped with such. Not installing damper may result in an exhaust moan/boom in the 2300-2500 rpm range.

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.