Some 1991-92 F-cars with 5.OL or 5.7L V-8 engines (RPOs LB9 or L98) and dual catalytic converter exhaust systems (RPO N10), may exhibit a metallic buzz or rattle that is most apparent during low speed/low load type operations.
The two causes indicated below may result in a metallic buzz/rattle noise:
Cause 1: Intermittent contact between the exhaust pipes just forward of the catalytic converter.
Cause 2: Air injector reactor (A.I.R.) pipe in contact with the toe pan to the front of the dash trim flange.
Correction 1: Install clamp, P/N 10041052, to the inboard exhaust pipe just rearward of the exhaust pipe to the catalytic converter extension pipe weld. As illustrated in Figure 1.
Correction 2: Reposition A.I.R. pipe to insure clearance of approximately 25 mm (1 inch) between the pipe and trim flange (reference Figure 2).
Part is currently available from GMSPO.
Labor Operation: T-1851
Labor Time: .3 Hr.
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.