EXHAUST ODOR COMPLAINTS 1986 'M' VAN

VEHICLES AFFECTED: 1986 'M' VAN WITH 4.3L TBI ENGINE (VIN CODE Z) and AUTOMATIC TRANSMISSION

Customer comments may be received regarding a rich exhaust odour on 1986 'M' Vans with 4.3L Throttle Body Injection (TBI) engines. This condition can be improved by installing a revised calibration PROM as listed below.

Service PROM Emission System Transmission

16068877 Federal Automatic

VIN Breaking Points are as follows,

Chev GMC

GB203188 GB524481

Use applicable labour operation:

NOTICE: This PROM will also reduce cold engine fast idle speeds from approximately 850 RPM to 750 RPM in drive.

Slight odour may still be present during warm-up, severe throttle maneuvers, or after wide open throttle applications. This is characteristic of systems equipped with three way catalytic converters. The vehicle should also be inspected to ensure no intake manifold or exhaust manifold leaks are present.

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.