Engine - Cold Rough Idle and Detonation

Number: 93-175-6E
Section: 6E
Date: APRIL 1993
Corporate Bulletin No.: 376504
ASE No.: A1, A8

Subject:
OLD ROUGH IDLE AND DETONATION

Model and Year:
1993 "M" VANS WITH 4.3L V6 ENGINE

CONDITION:

Some owners of 1993 model year M vans equipped with LB4 4.3L V6 VIN Z (NOT L35 VIN W) may report a rough idle or shake during engine warm-up and/or detonation during normal engine operation. Vehicles built before the following VIN breakpoint are affected: PB177872

CAUSE:

Idle Shake - Engine idle speed causing undesirable body vibration during warm-up. Detonation - ESC system retard rate may be too slow.

CORRECTION:

A calibration has been developed to minimize the time the engine operates at the speed where the vibration can occur. The calibration also contains enhancements to the ESC system that will lessen the possibility of detonation.





Parts are expected to be available on April 12, 1993.

WARRANTY INFORMATION:
Labor Operation: T0500 - PROM Replace
Labor Time: 0.6 hour