Engine - Driveability/Exhaust Odor/Emission Testing
88chevy10Number: 88-235-6E
Section: 6E
Date: MAY, 1988
Subject: DRIVEABILITY, EXHAUST ODOR, INSPECTION/MAINTENANCE TESTING
Model and Year: 1987-88 C/G/K/M/R/V TRUCKS EQUIPPED
WITH 4.3L (VIN CODE Z) ENGINE
TO: ALL CHEVROLET DEALERS
This bulletin cancels and supersedes Chevrolet Dealer Service bulletin #87-256-6E, dated January, 1988. All copies should be destroyed.
This bulletin expands the application to include 1987 and 1988 C, G, K, R, V trucks, all 1987 M vans, and 1988 M vans prior to VIN 191855.
Some 1987 and 1988 vehicles equipped with 4.3L engines (VIN Code Z), including 1988 M vans with VIN's prior to those listed above, may exhibit one or more of the conditions listed below.
NOTICE: 1988 M VANS BUILT AFTER THESE VIN's ARE EQUIPPED WITH AN OXYGEN SENSOR LOCATED IN THE EXHAUST Y-PIPE AND AN APPROPRIATE CALPROM. CALIBRATION PROMS ARE PARTICULAR TO OXYGEN SENSOR LOCATION AND SHOULD NOT BE INTERCHANGED. CALIBRATION PROMS LISTED IN THIS BULLETIN ARE APPROPRIATE FOR VEHICLES WITH THE OXYGEN SENSOR LOCATED IN THE EXHAUST MANIFOLD ONLY. ALSO, A BLEED CONNECTOR SHOULD NOT BE INSTALLED IN A VEHICLE EQUIPPED WITH AN OXYGEN SENSOR LOCATED IN THE Y-PIPE AS AN OVER RICH CONDITION WITH INCREASED SULFUR ODOR AND DEGRADED DRIVEABILITY MAY RESULT.
Driveability Conditions
- Driveability sag or hesitation during the first five minutes of operation after a cold start or within one minute of operation after a hot restart.
- Surge at speeds of 40-50 mph during a cruise or light throttle application.
- Long crank time or false start after a 1-3 hour hot soak
Inspection/Maintenance Testing
- Difficulty in meeting state exhaust emission inspection/maintenance testing requirements.
Exhaust Odor Condition
- Hydrogen sulfide smell typically described as "rotten egg smell" at idle.
Service Procedure
If a vehicle, exhibiting one or more of the conditions described, can not be repaired by using normal service procedures, the following should be performed:
Condition Service Procedure
Driveability Use a "Scan" tool to check PROM
I.D., determine if the vehicle has the appropriate calibration PROM as listed in the table below. If the vehicle is not equipped with the calibration PROM listed, install the PROM specified.
Inspection/Maintenance Use a "Scan" tool to check PROM
I.D., and/or Exhaust determine if the vehicle has the
Odor appropriate calibration PROM as
in the table below. If the vehicle is not equipped with the calibration PROM listed, install the PROM specified.
In addition, install bleed orifice connector, P/N 10105820 per the instructions on page 4 of this bulletin.
Calibration PROM Table
Federal/Altitude Emissions Packages (NA5 and NA6)
California Emissions Packages
FIGURE 1 - MODEL 220 TBI:
Bleed Orifice Installation Procedure
1. Disconnect the EGR vacuum line currently on port "J" on the front of the TBI unit. See Figure 1.
2. Install connector bleed assembly, P/N 10105820 on port "J" of the TBI unit.
3. Reconnect the EGR vacuum line remove from port "J" to the open end of the connector bleed assembly.
Labor Operation Labor Description
Number Time
T7455 .3 Hours Identify existing PROM
and install connector bleed assembly.
Add .2 Hours To change PROM if
necessary.