K 3500 Truck 4WD V8-454 7.4L VIN J SFI (1996)
Intake Manifold: Customer Interest
Rough Idle, Low Power, Hesitation, Lean Engine, DTCs Set
File in Section: 6 - Engine
Bulletin No.: 67-61-16
Date: May, 1996
Subject:
Rough Idle, Lack of Power, Miss, Hesitation, Whistle, Lean Engine, DTC P0171, P0174, P0300, P0507 or Loose Upper Intake Manifold Bolts
(Replace Gaskets and Torque With New Sequence)
Models:
1996 Chevrolet and GMC C/K, P Models
with 7.4L Engine (VIN J - RPO L29)
Condition
Some owners may comment of an engine whistle or noise, hesitation, lack of power or rough idle. This could be accompanied by a lean engine condition
or higher than desired engine idle. The vehicle could also contain stored Diagnostic Trouble Codes P0171, P0174, P0300 or P0507.
Cause
The gasket between the upper and lower intake manifolds relaxes resulting in a loss of bolt torque. This in turn can disrupt the gasket seal allowing an air
leak into the manifold assembly.
Correction
A revised torque sequence, torque values and use of a threadlocker on the upper intake manifold bolts has been issued to correct this problem.
Use the procedure from the appropriate service manual on vehicle repair section to replace the gaskets between the upper and lower intake manifold,
EXCEPT APPLY THREADLOCKER and use the torque sequence in place of the torque shown in the service manual.
THE TORQUE VALUES AND SEQUENCE IN THE SERVICE MANUAL HAVE BEEN REVISED AND THE USE OF A THREADLOCKER HAS
BEEN ADDED. USE THE TORQUE VALUES AND SEQUENCE IN THIS BULLETIN.
BE SURE THAT ALL GASKET MATING SURFACES ARE CLEAN AND FREE FROM OIL AND RESIDUE. INTAKE MANIFOLD SHOULD BE
COOL, NOT HOT BEFORE SERVICING.
Torque Procedure
1.
Coat a minimum of 8 lower threads of the bolt with Loctite(R) 242 (GM P/N 12345382).
2.
Torque all bolts in sequence to 16 N.m (12 lb ft).
3.
Torque all bolts in sequence to 24 N.m (18 lb ft).
4.
Check all bolts in sequence to assure all bolts are torqued to 24 N.m (18 lb ft).
