Engine - Surge Under Light Throttle at High Altitude

90chevy34
GMC NUMBER: 90-6E-109

GROUP: 6E ENGINE EMISSION

DATE: OCTOBER, 1990

CORPORATE
NUMBER: 036516
SUBJECT: SURGE UNDER LIGHT THROTTLE CRUISE/COAST AT HIGH ALTITUDE

MODELS: 1990 S/T LIGHT DUTY TRUCKS WITH 4.3L ENGINES AND 5LM60 MANUAL TRANSMISSIONS
CONDITION:
Owners of some 1990 4.3L S/T trucks equipped with 5-speed manual transmissions may comment about an engine surge condition at light throttle cruise or coast while driving at altitudes above 4500 ft.

CAUSE:
This condition is related to EGR at low barometric pressures.



CORRECTION:
To correct this condition, install a new ECM (P/N 16144288) and calibration PROM in the truck. The new calibration PROM revises the EGR calibration for high altitude driving conditions. Use the application chart below to select the proper PROM.
NOTE: All of the following PROMs must be used with ECM (P/N 16144288).
Parts are currently available from GMSPO.

WARRANTY INFORMATION
Labor Operation: T0500

Labor Time: .8 hrs.