Engine - Detonation/Sulfur Odor From Exhaust

91chevy16

GMC NUMBER: 90-6F-125

GROUP: 6F Engine Exhaust

DATE: July, 1991

CORPORATE
NUMBER: 136511


SUBJECT: DETONATION AND/OR EXHAUST ODOR (INSTALL NEW PROM)

MODELS: 1990 C/K, R/V, G, and P TRUCKS WITH 7.4L ENGINES (ABOVE 8600 GVW)


Condition: Some owners of 1990 trucks with the 7.4L engine may comment of either detonation at highway speeds or exhaust odor (sulfur smell) at idle.

Cause: The original spark advance and idle calibration may generate detonation or sulfur odor comments for a few isolated conditions.


Correction: On trucks where these conditions can not be repaired using normal service procedures, a revised calibration PROM should be installed (see below).


Part Number Emission System Trans. PROM Broadcast Scanner ID
16165446 NA4 (above 8600 GVW) M40 (Auto) AYKK 5451
16165447 NA4 (above 8600 GVW) M20 (Manual) AYKL 5461

Labor Operation Number: T0500

Labor Time: .6 Hour