Intake Air Duct - Reduced Engine Performance
90chevy34GMC NUMBER: 91-6-44
GROUP: 6 Engine Diagnosis
DATE: December, 1990
CORPORATE
NUMBER: 066001
SUBJECT: REDUCED ENGINE PERFORMANCE
MODELS: 1988-91 C/K LIGHT DUTY TRUCKS - ALL ENGINES
Figure 1:
Figure 2:
Some 1988-91 C/K light duty trucks may experience a condition of reduced engine performance in warmer climates during heavy usage or towing. This condition may be caused by a collapsed air duct inside the right front fender (see Figure 1) resulting in a collapsed flexible duct at the air cleaner assembly (see Figure 2). Vehicles that are diagnosed as exhibiting this condition may be repaired by replacing the collapsed duct with a new duct assembly made of a new material. New duct assemblies can be identified by the part number located on the part. Also on models equipped with 7.4L engines it will be necessary to add a strap to improve the retention of the duct to the air cleaner assembly (see Figure 2).
VEHICLES INVOLVED The condition was corrected in production effective with the following VIN breakpoints:
Figure 2:
SERVICE PROCEDURE
1. Remove resonator hold down strap (see Figure 2).
2. Remove resonator and rear air intake duct.
3. Remove duct adapter from fender.
4. Remove engine coolant reservoir.
5. Remove underhood retractable light assembly (if equipped).
6. Remove battery cables, battery hold down bolt and remove battery from vehicle.
7. Remove ground strap bolt at fender.
8. Remove inner fender duct front retaining screw from fender.
9. Remove inner fender duct rear fastener from fender.
10. Remove inner tender duct assembly from fender.
11. Install new inner fender duct assembly in fender.
12. Install inner fender duct rear fastener.
13. Install inner fender duct front retaining screw.
14. Install ground strap bolt to fender.
15. Install battery, battery hold down bolt and battery cables.
16. Install underhood retractable light assembly (if equipped).
17. Install engine coolant reservoir.
18. Install duct adapter to fender.
19. Install resonator and resonator hold down strap.
20. Install new rear air intake duct.
21. Install new rear air intake duct strap (7.4L only).
SERVICE PARTS INFORMATION
Parts are expected to be available on December 17, 1990. Until then, normal part orders will not be accepted by GMSPO. Only verifiable emergency VIP orders will be accepted. GMSPO will make every effort to obtain parts. All parts will be placed on 400 control to waive VIP surcharges. However, the parts will be shipped premium transportation at dealer's expense. All other order types will be canceled as incorrectly ordered while 400 control is in place.
WARRANTY INFORMATION For vehicles repaired under warranty use: