Engine - More Than Normal Detonation

9232OLDS03

NUMBER: 91-T-192A

CORP.REF.NO: 136517R

DATE: May 1992

SECTION: 6E2, L4


SUBJECT
ENGINE DETONATION
- INSTALL NEW PROM PACKAGE


MODELS/YEARS
1990-91 CUTLASS CALAIS WITH
AUTOMATIC TRANSAXLE AND 2.5L (VIN U) ENGINE


This bulletin cancels and replaces Dealer Technical Bulletin 91-T-192 which should be discarded.

CONDITION:
Some owners of 1990-91 Cutlass Calais may comment about more than normal engine detonation. This level of detonation is more than the burst detonation that is inherent with the 2.5L (VIN U) engine at off-idle tip-in at elevated coolant temperatures. Detonation may occur as steady state detonation, detonation on a slight grade or detonation on a light acceleration. Prior attempts to correct this detonation may include the use of top engine cleaners, decarboning or installation of a new head gasket. However, the detonation will return in a short amount of mileage.

CAUSE:
The octane requirement of the engine increases with mileage. Therefore, original spark calibration may produce detonation in some vehicles.

CORRECTION:
The correction for this condition is a new PROM package. This PROM will modify the spark tables and raise the Torque Converter Clutch (TCC) engagement point to 44 MPH. THE CUSTOMER SHOULD ALSO BE ADVISED THAT THIS PROM MAY HAVE A NEGATIVE IMPACT ON FUEL ECONOMY.

Note:
Dealer Technical Bulletin 90-T-196 is still effective for a chuggle only condition.

1990 1991
The new PROM Package P/N is: 16168732 16176078
Broadcast Code: AZBH BATT
Scanner ID: 8791 6081

Parts are currently available from GMSPO.

WARRANTY INFORMATION:
Labor Operation: T0500
Labor Time: 0.3 Hour
Trouble Code: 92