EXHAUST ODOR COMPLAINTS REDUCES COLD FAST IDLE SPEED

EXHAUST ODOUR - INSPECTION/MAINTENANCE (I/M) TESTING

VEHICLES AFFECTED: 1986 "M" VANS EQUIPPED WITH LB4 ------------------ 4.3L ENGINES (ENGINE CODE Z)

THIS REVISION MODIFIES THE SERVICE PROCEDURE IN PRODUCT SERVICE BULLETIN 86- 643-103 DATED SEPTEMBER 22/86 BY THE ADDITION OF A CONNECTOR BLEED ASSEMBLY AND EXPANDS THE APPLICABLE USAGES TO INCLUDE VEHICLES EQUIPPED WITH MANUAL TRANSMISSIONS.

Customer with M-vans equipped with LB4 4.3L engines (engine Code Z) may experience a hydrogen sulfide related odour typically described as "rotten egg smell" at idle.

If the condition can not be repaired using normal service procedures, a revised calibration PROM and a connector bleed assembly, P/N 10093100, may be installed. See the service PROM usage chart below for the appropriate service PROM part number.

SERVICE PROM USAGE ------------------ PROM, P/N --------- Federal Emission Automatic 4-Speed 16068877 Federal Emission Manual 5-Speed GM8/F90 axle 16068942 Federal Emission Manual 5-Speed GU4/GU6 axle 16068952

Installation Procedure:

1. Disconnect the negative battery cable.

2. Install the appropriate service PROM,

3. Disconnect the cap or vacuum line currently on port J on the front of the TBI unit.

4. Install connector bleed assembly, P/N 10093100, by sliding the rubber end on to port J.

5. Connect the vacuum line or cap removed from port J to the open end of the connector bleed assembly.

6. Reconnect the negative battery cable.

Labour Operation Number: T7430 Labour Time : .4 Hours

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.