Firenza L4-121 2.0L VIN K TBI (1987)
PROM - Programmable Read Only Memory: All Technical Service Bulletins
Engine Control - Driveability/Codes 23, 25, 33, 34
NUMBER: 88-T-147B
CORP. REF. NO: 936518R
DATE: April 1990
SECTION: 6E
SUBJECT:
DRIVEABILITY CONDITIONS - 2.8L AND/OR STORED ENGINE CODES 23, 25, 33 OR 34, (PROCEDURE AND PROM)
MODELS/YEARS:
1987-88 FIRENZA AND CUTLASS CIERA, 1988 CUTLASS SUPREME
This bulletin has been revised to change the Memcal P/N, Scanner I.D. and Broadcast Code for the manual transmission vehicles.
This bulletin has been updated by bulletin 88T147C, 5/90.
This bulletin cancels and supercedes Dealer Technical Bulletin 88-T-147A which may be discarded.
Some customers with an engine/vehicle combination listed below
1987 Firenza Models With a 2.8L Engine (Vin Code W) 1988 Cutlass Supreme Models With a 2.8L Engine (Vin Code W) 1987-88 Cutlass Ciera
Models With a 2.8L Engine (Vin Code W) may comment that they have experienced one or more of the following conditions:
A cold start stall or sag,
A decel stall
A tip-in hesitation
A check engine light with stored Codes 23, 25, 33, 34 or
An engine speed flare during a declutch operation with a manual transmission equipped vehicle.
These conditions may be attributed to a number of components/interactions. In the interest of simplifying diagnosis and repair, the following 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, and/or a stored Code 33 or 34 is found, then complete the
following procedure:
1.
Perform diagnostic procedures per Section 6E of the Service Manual, and correct any faults except for Codes 33, 34, 23 or 25. If the diagnostics
indicate the Mass Air Flow (MAF) is to be replaced or a Code 33 or 34 is present, DO NOT REPLACE THE MAF SENSOR! Proceed to Step #
3. If a Code 23 or 25 is present, go to Step # 2 below. PROCEED TO STEP # 3 ONLY IF NORMAL DIAGNOSTIC CHECKS DID NOT
IDENTIFY A CAUSE FOR THE CUSTOMER CONCERN.
2.
If a Code 23 or 25 is stored, perform the model year diagnostics for the Manifold Air Temperature Sensor (MAT). If the diagnostics indicate that
the MAT is faulty and replacement is required, replace the combination MAT/MAF sensor. Proceed to Step # 3.
