COLD START STALL/HESITATE IDLE ROLL (DIAG. NEW HEI AND MEMCAL

Subject: COLD START STALL/HESITATION IDLE ROLL AND UPSHIFT SAG (DIAGNOSTICS, NEW HEI MODULE AND MEMCAL)

Models Affected: 1990-92 FIREBIRD MODELS WITH 3.1

THIS BULLETIN HAS BEEN REVISED TO ADD THE 1992 MODEL YEAR, THE ADDITION OF TWO "IMPORTANT" STATEMENTS, TO ELIMINATE THE VIN BREAKPOINTS AND TO CHANGE THE MEMCAL INFORMATION WITH THE ADDITION OF THE M/T. THIS BULLETIN CANCELS AND REPLACES BULLETIN 91-6-32 ISSUED 3191. PLEASE DISCARD BULLETIN 91-6-32.

Condition:

--------- Some customers may experience Cold Start Stall and/or Hesitation, Idle Roll and/or 1-2 Upshift Sag with their 1990-92 Firebird models.

Cause:

----- System and component variability and electromagnetic interference.

Correction:

---------- If any of the subject conditions are found, complete the following procedure:

1. Perform diagnostics, per Section 6E of the Service Manual. Make any adjustments as required, or replace any defective parts associated with the above conditions.

Important: The customer should avoid the use of high octane fuels as they do not increase performance.

2. Replace the High Energy Ignition (HEI) module with a new P/N 16140039, and install a new Mem-Cal from the table, using the Service Manual and attached procedure.

Important: The appropriate model year cartridge must be used to check new MEMCALS.

Broadcast Scanner Part Code I.D. Number Description --------- ------- ------ ----------- AZTY 1331 16171406 MEMCAL (FED-AUTO)

AZTX 1321 16171410 MEMCAL (CALIF-AUTO)

BAWX 6651 16176864 MEMCAL (NATIONWIDE- MANUAL)

A. Pull the underhood Electronic Control Module (ECM) continuous power fuse or disconnect the battery and leave it disconnected for at least 1 minute.

B. Remove existing Mem-Cal and install a new service Mem-Cal per the latest service procedure.

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 transmission to "Drive".

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 transmission to "Drive".

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

3. If the installation of the new parts does not eliminate the driveability conditions, then the ECM harness and the electrical harness (near the coil bracket) should be inspected for chafing and repaired as required.

Parts are expected to be available on May 11, 1992. In case of limited inventory, parts will be placed on 400 Control to waive VIP surcharges. Only verifiable emergency VIP orders will be accepted. SPO will make every effort to obtain parts. However, the part will be shipped premium transportation at dealer's expense and all other order types will be placed on backorder until the 400 control is removed.

Labor Operation Number: T1707 Labor Time : 1.2 Hour Add : 0.5 Hour (To inspect and repair wire harness as as necessary)

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.