ENGINE STALL AND/OR HES. AFTER COLD START

VEHICLES AFFECTED: 1987-89 F-CARS W/2.8L MPFI AND A/T

Some owners of 1987-89 F-cars with a 2.8L multi-port fuel injected (MPFI) engine (VIN Code S) and an automatic transmission may experience an engine stall after cold start or during a Park to Drive/Reverse maneuver immediately after the cold start, or a cold driveaway hesitation. These conditions may occur during emission ambient temperatures of 18-27 DEG Celsius (65-80 DEG Fahrenheit).

To service either of these conditions, complete the diagnostic procedures per Section 6 of the Service Manual. Specific attention should be given to the following items and repair as required.

1. Loose or leaking air duct between mass airflow (MAF) sensor and throttle body.

2. Low minimum air rate.

IMPORTANT: Reference Section 6E3-C2 of the Service Manual for the proper minimum air rate adjustment procedure and specification.

3. Openings in the EGR transfer tube.

IMPORTANT: The EGR transfer tube connects the EGR valve assembly to the exhaust manifold.

4. The correct service PROM calibration for 1987-88 vehicles.

IMPORTANT: Reference the chart below for 1987-88 2.8L F-car with four-speed automatic transmission, service PROM part numbers:

1987-88 1987-88 Emission *PROM Service PROM BROADCAST Model System I.D. Part Number CODE ----- ------ ---- ----------- ---- Camaro Federal 0501 16130659 APFR Firebird Federal 0531 16130708 APFU

* PROM identification as read with a service scan tool.

5. Fouled spark plugs or loosely attached ignition wires at the distributor or spark plug (diagnosis to be completed using an oscilloscope or equivalent).

6. A plugged or damaged catalytic converter system.

IMPORTANT: Inspect exhaust system for any restrictions, per Section 6F of the Service Manual.

7. A defective cold start injector (reference Section 6E3-C2 of the Service Manual).

8. A plugged, leaky, or damaged fuel injector (reference Section 6E3-C2 of the Service Manual.

IMPORTANT: Fuel injectors should hold 20-40 psi fuel pressure for a period of 20 minutes after engine off. An injector balance test will detect plugged or damaged injectors.

If the stall or hesitation condition persists, after a thorough inspection has been completed, then replace the PROM and install an air injection service kit. The PROM will allow a richer fuel mixture, for improved driveability, and the air injection reaction (A.I.R.) system will allow the richer system to pass emission requirements. The A.I.R. system hardware and detailed installation instructions may be obtained by ordering service kit, P/N 10115773. Refer to the following chart to obtain the new service PROM part number.

Emission PROM Service PROM Broadcast Model System I.D. Part Number Code ----- ------ ----- ----------- ---- Camaro Federal 6221 16136127 ARJK Firebird Federal 6231 16136128 ARJL

IMPORTANT: The above service PROMs and A.I.R. system parts are for a 2.8L F-car with an automatic transmission only.

After installation of the A.I.R. service kit has been completed, a new vehicle emission control label should be installed on the vehicle. Reference the chart below for the proper emission label part number.

OLD LABEL NEW LABEL YEAR MODEL PART NUMBER EMISSION SYSTEM PART NUMBER ---- ------ ------------ ---------------- -----------

1987 Camaro 10051417 Federal 10145422 10051481 10145422

1987 Firebird 10051418 Federal 10145423 10051482

1988 Camaro 10055677 Federal 10145426 10055678

1988 Firebird 10055679 Federal 10145427 10055680

1989 Camaro 10116634 Federal 10145430

1989 Firebird 12016635 Federal 10145431

IMPORTANT: Current label must be removed and the surface cleaned prior to installation of the new label.

Labour Operation Number: T1420

Labour Time 6.6 Hours (1987-88)

6.8 Hours (1989)

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.