EXHAUST ODOR COMPLAINTS REDUCES COLD FAST IDLE SPEED

MODELS: 1986 M VANS EQUIPPED WITH 4.3L (VIN CODE Z) ENGINES

THIS BULLETIN CANCELS AND SUPERSEDES TRUCK SERVICE BULLETIN 86-B-115/ CHEVROLET BULLETIN 86-149 DATED AUGUST, 1986, ALL COPIES OF WHICH SHOULD BE DESTROYED.

THIS REVISION MODIFIES THE SERVICE PROCEDURE BY THE ADDITION OF A CON- NECTOR BLEED ASSEMBLY AND EXPANDS THE APPLICABLE USAGES TO INCLUDE VEHICLES EOUIPPED WITH MANUAL TRANSMISSIONS.

Some 1986 M vans equipped with 4.3L TBI engines (VIN Code Z) may experience one or both of the following conditions:

1. Hydrogen sulfide related odor typically described as "rotten egg smell" at idle.

2. Difficulty in meeting state exhaust emission inspection/maintenance (I/M) testing requirements.

If these conditions cannot 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 Automatic 4-Speed 16068877 Emission Calif Automatic 4-Speed 16068926 Emission

Federal Manual 5-Speed 16068942 Emission 2.56/2.73 axle Federal Manual 5-Speed 16068952 Emission 3.08/3.42 axle Calif Manual 5-Speed 16068946 Emission 2.73 axle Calif Manual 5-Speed 16068956 Emission 3.08/3.42 axle

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. (See Figure No . 1).

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.

Labor Operation Number: T7430

Labor Time: .4 Hour

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.