COLD START STALL-CHUGGLE AT 35-45 MPH WITH TCC. Buick Riviera 1990

SUBJECT: COLD START STALL AND/OR CHUGGLE AT 35-45 MPH WITH TORQUE CONVERTER CLUTCH ENGAGED (REVISED CALIBRATION MEM-CAL)

MODELS AFFECTED: 1989-91 PARK AVENUE/ULTRA AND LESABRE MODELS WITH 3800 (CODE C) ENGINES ONLY

Some owners of 1989 through 1990 Park Avenue/Ultra and 1989-1991 LeSabre models equipped with the 3800 (Code C) engine may experience one or both of the following conditions:

o Engine does not stay running on initial cold start.

o Chuggle at 35-45 mph with torque converter clutch engaged.

The two conditions are independent of each other, yet it may be possible for both conditions to exist on one vehicle.

Follow the information outlined under the individual heading for that condition:

ENGINE DOES NOT STAY RUNNING ON INITIAL COLD START

If the vehicle's basic engine controls and fuel systems are operating properly, it is important for the technician to be familiarized with information contained in Service Bulletin 91-6E-3, "Recommended fuels for non-turbo port fuel injection engines". If the condition cannot be repaired by changing fuel or using currently published service and diagnostic procedures, it may be necessary to install a revised calibration MEM-CAL. Install MEM-CALS listed in Table A for this condition only.

CHUGGLE AT 35-45 MPH WITH TORQUE CONVERTER CLUTCH ENGAGED

Proceed with the diagnostic flow chart (Figure 1) to aid in identifying the possible cause of the condition.

Note: The new revised calibration MEM-CALS may affect fuel economy. Be sure to advise the vehicle owner of this fact.

ENGINE DOES NOT STAY RUNNING ON INITIAL COLD START AND CONVERTER CLUTCH ENGAGED CHUGGLE AT 35-45 MPH AND WITH TORQUE -------------------------------------------------------------- Should owners' comments indicate both conditions exist. Follow steps outlined in both procedures. The two conditions are independent of each other. If it is determined that a new revised calibration MEM-CAL is necessary to correct both conditions, select MEM-CALS listed in Table B.

Note: The new revised calibration MEM-CALS in Table B may affect fuel economy. Be sure to advise the vehicle owner of this fact.

TABLE "A"

SCANNER ID WITH BROADCAST SERVICE YEAR MODEL AXLE RATIO MEM-CAL INSTALLED CODE PART # ------- ------------ ---------- ----------------- ------- -------- 1989-90 Park Avenue/ 2.84 5614 AYLA 16165848 Ultra NATL/CALIF 1989-91 LeSabre

1989-90 Park Avenue/ 2.97 5634 AYLC 16165839 Ultra NATL/CALIF 1989-91 LeSabre

TABLE "B"

1989-90 Park Avenue/ 2.97 5644 AYLD 16165829 Ultra NATL/CALIF 1989-91 LeSabre

Parts are currently available from GMSPO.

WARRANTY INFORMATION:

Labor Operations No.: T0500 Labor Time: .7 Hr. (Replace MEM-CAL) .2 Hr. (Add to complete chuggle Diagnostic Flow Chart Only)

Object Number: 77969 Size: LF

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.