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

Subject: INFORMATION ON EXHAUST RATTLE/RINGING NOISE

Models Affected: 1991-92 GRAND PRIX MODELS WITH 3.4L V-6 ENGINE (RPO LQ1)

This bulletin provides information regarding a potential customer concern of an audible noise condition that may be perceived as a metallic rattle/ringing on some 1991-92 Grand Prix models with 3.4L V-6 engines (RPO LQ1).

Condition:

--------- 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.

Do not attempt any modifications or repairs to the engine and/or exhaust system to correct this condition.

This information is being conveyed to keep car dealers and customers informed and to alleviate any unnecessary repairs.

When repair information becomes available, this bulletin will be updated.

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.