EXHAUST SYSTEM BACKFIRING (AIR CONTROL VALVE ASSEMBLY)

VEHICLES AFFECTED: 1984-85 1.6L (L17) Engine With Leaded Fuel Option (RPO NM8)

The backfire phenomenon may occur with some vehicles under the following circumstances:

- during extended decelerations from high engine speeds with transmission clutch engaged - during warm-up periods - at high elevations

NOTE: Before implementing the following procedure, perform relevant system performance click as outlined in the Shop Manual, and ensure the engirie is adequately tuned to the tune-up label specification.

1. Delete the intake manifold vacuum signal to the air control valve assembly located behind the air pump assembly (see attached diagram).

2. Cap the intake manifold fitting and the air control valve assembly openings with rubber caps, Part Numbers 3928101 and 343350, respectively.

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.