G 2500 3/4 Ton Van V6-262 4.3L VIN Z (1992)
PROM - Programmable Read Only Memory: Customer Interest
PROM - Sustained Detonation/Knock
Group Ref.: Engine Fuel & Emissions
Bulletin No.: 376508
Date: October, 1993
SUBJECT:
SUSTAINED DETONATION/KNOCK (APPLY STANDARD DIAGNOSTIC PROCEDURE/INSTALL NEW PROM)
MODELS:
1992 C/K AND S/T TRUCKS, G AND M/L VANS
THIS BULLETIN IS BEING REVISED TO CORRECT THE SERVICE PROM KIT NUMBERS FOR THE FEDERAL C (BHSM) AND THE
CALIFORNIA C (BHUT) CALIBRATIONS. PLEASE DISCARD PREVIOUS DIVISIONAL PUBLICATIONS:
CHEVROLET
92-285B-6E
GMC TRUCK
92-6E-162
GM OF CANADA
93-6E-128
CONDITION:
Some owners of 1992 S/T, C/K, M/L or G trucks equipped with 4.3L (LB4) V6 (VIN Z) engines may comment that the engine exhibits sustained
detonation (knock) during acceleration or climbing a grade. The sustained detonation (knock) occurs after the engine reaches normal operating
temperature. The detonation may occur at part throttle or wide open throttle operation.
NOTE:
Some burst detonation (knock) during "tip-in" acceleration and/or at shift points is considered normal.
CAUSE:
Some engines may have higher than intended compression ratios after accumulating carbon deposits.
CORRECTION:
