V 3500 P/U 4WD V8-454 7.4L VIN W 4-bbl (1988)
ASE No.: A1 & A8
Subject:
ENGINE DRIVEABILITY - SURGE HOT/COLD, DETONATION
Model and Year:
1987-89 C/K, R/V AND G/P TRUCKS WITH 7.4L ENGINE
THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN NUMBERS 88-162-6E, DATED AUGUST 1988; 88-195-6E,
DATED MAY 1988; AND 89-263-6E, DATED OCTOBER 1989. ALL COPIES OF 88-162-6E, 88-195-6E AND 89-263-6E SHOULD BE
DISCARDED.
Condition:
Some owners of 1987-89 C/K, R/V and G/P trucks with 7.4L engine may experience the following:
1.
Surge on acceleration and/or at road load speeds
2.
False Service Engine Soon Light - Code 32 (EGR)
3.
Poor driveability during warm up
4.
Detonation under load
Correction:
1.
On 1987-89 models, check for vacuum leaks including:
A.
TBI Base gasket to adapter
B.
TBI Adapter to TBI
C.
Re-torque intake manifold to 30 lbs.ft.
2.
On 1987-89 models, check base timing (Spec. 4 degrees BTDC).
View A
3.
On 1987-88 models only, relocate Map Sensor to Air Cleaner.
A.
Check Map Sensor operation using procedures on Page 3-122 and 3-123 of the 1991 Fuel and Emission Manual, replace sensor if necessary.
B.
Disconnect vacuum tube assembly and electrical connection from Map Sensor.
