REDUCED ENGINE PERFORMANCE NEW STYLE AIR DUCTS
SUBJECT: REDUCED ENGINE PERFORMANCE (NEW AIR DUCTS)
VEHICLES AFFECTED: ALL 1988-91 C/K TRUCKS
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 refer to Figure 1 resulting in a collapsed flexible duct at the air cleaner assembly refer to 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 as shown in Figure 2).
VEHICLES INVOLVED
The condition was corrected in production effective with the following VIN breakpoints:
1990
Fort Wayne GMC LZ542249 CHEVROLET LZ236324
Pontiac East GMC LE540684 CHEVROLET LE221927
1991
Oshawa GMC M1504007 CHEVROLET M1111879
SERVICE PROCEDURE
1. Remove resonator hold down strap refer to 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 fender 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
Part Number Description Quantity Application ----------- ----------- -------- ----------- 15667232 Duct - Inner fender 1 1988-91 All Engines
15657356 Duct - Rear Air Intake 1 1988-90 5.OL W/K46 (pre-cleaner) 1 1988-91 5.7L, 6.2L
15657357 Duct - Rear Air Intake 1 1988-90 7.4L
15657359 Duct - Rear Air Intake 1 1991 7.4L
15657358 Strap - Rear Air Intake 1 1988-91 7.4L Duct
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.
