DRIVEABILITY CONCERNS (DIAGNOSIS AND NEW MEMCALS)

Model and Year: 1990 W Car With 3.1L (VIN Code T) Engine

DEALER SERVICE BULLETIN 90-33-6E, DATED JULY 1989, IS BEING CANCELLED AND SUPERSEDED BY THIS BULLETIN WHICH SPECIFIES PROCEDURES OUTLINED ARE NOT TO BE USED ON VEHICLES WITH 'DIGITAL' EGR VALVES. ALL COPIES OF 90-33-6E SHOULD BE DISCARDED.

IMPORTANT: THIS BULLETIN IS NOT TI BE PERFORMED ON ENGINES WITH A "DIGITAL" EGR VALVE. "DIGITAL" EGR VALVES ARE IDENTIFIED BY THE 3 SOLENOID TOWERS ON TOP OF THE VALVE.

Some customers with an engine/vehicle combination listed above may comment that they have experienced one or more of the following conditions:

A cold start stall or sag, A decel stall, or A tip-in hesitation.

These conditions may be attributed to a number of components/inter-actions. In the interest of simplifying diagnosis and repair, the followlng procedure has been developed to reduce system sensitivity, thereby addressing a variety of potential causes simultaneously.

If a customer comment concerning an occasional engine stall or a drive hesitation is received, then complete the following procedure:

1. Perform diagnostic checks, per Section 6E3 of the Service Manual and replace any defective components.

Proceed to Step #2 only if diagnostic checks uncover no cause for the customer comments.

2. Check the MEM-CAL scanner I.D. to determine if latest MEM-CAL is installed. If not, proceed to Step #3. If so, the vehicle must be reinspected for other possible causes for the problem.

3. Install a new MEM-CAL into the Engine Control Module (ECM) per instructions below. The new MEM-CAL may be ordered from GMSPO. See the attached service part number chart.

A) Pull the under-hood ECM continuous power fuse or disconnect the battery and leave it disconnected for at least 10 minutes.

B) Remove current MEM-CAL and install a new service MEM-CAL.

C) Restore the battery power and place air conditioning controls (if equipped) in the 'off' position.

D) Firmly apply the parking brake and block the drive wheels. Start the engine, and shift the transaxle to 'drive' for automatics or 'neutral' for manuals.

E) Allow the engine to run until the engine cooling fan has cycled once, or a maximum of 10 minutes.

F) Turn the ignition key to the 'off' position for at least 5 seconds.

G) Start the engine, and shift the transaxle to 'drive' for automatice or 'neutral' for manuals.

H) Allow engine to run for at least 5 minutes.

Use Labor Operation Number: T1506

Labor time: .7 Hour

1989-1990 W-CAR 3.1L ENGINE MEM-CAL SELECTION CHART - SERVICE PART NUMBERS

MODEL MODEL EMISSION MEM-CAL SCANNER BROAD- YEARS TYPE TRANS. CONFIG. P/N I. D. CAST ---- ---- ------ ------- --- ----- CODE ---- 1990 W AUTO 3-SPEED FED 16138526 8471 ARZX

1990 W AUTO 4-SPEED FED 16138522 8461 AFZW

Parts are currently available.

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.