DIESEL ALTITUDE ADJUSTMENT ADJ. TO IMPROVE PERFORMANCE

The 1983 Oldsmobiles equipped with 5.7L V-8 diesel engines will be manufactured with either high or low altitude diesel systems. A vehicle with a high altitude system will be invoiced with option NA6. The type of system can also be identified by the emission label attached to the fan shroud. The label will indicate that the vehicle was designed for principal use at either high or low altitude.

These adjustments are considered Altitude Performance Adjustments and apply only to in-use vehicles. They should not be used to modify vehicies prior to sale.

Dealers must not sell vehicles with low altitude systems for principal use at high altitude.

CONVERSION OF LOW ALTITUDE SYSTEM TO HIGH ALTITUDE

Dealers in high altitude areas should encourage owners who have moved to high altitude counties to purchase the service adjustment procedure outlined below, which is considered an owner maintenance expense. See attachment for a list of counties which the Environmental Protection Agency has designated as high altitude counties. Diesel timing should be checked or adjusted at the same approximate altitude at which the vehicle will be driven.

1. Replace the EGR vacuum control valve assembly (Figure 1) with the assembly shown in the parts information.

2. Install timing meter J-33075 or equivalent, set pump timing - 4 DEG, and set idle speed to specifications.

3. Remove air cleaner and air crossover assemblies and install screen covers J-26996-2.

4. Install shop towel in the intake manifold valley area under the injection pump head to absorb any full leakage. Remove housing pressure tap plug and seal located on the rear of the pump (Figure 2).

5. Using the parts contained in kit, part number 22516487 or equivalent, assemble locknut and new seal (O-ring) to metering valve stop screw.

6. Install assembly in injection pump until locknut contacts pump housing. Tighten locknut.

7. Place transmission in Park, turn A/C off and start engine.

8. Loosen locknut and slowly turn metering valve stop screw clockwise until idle speed drops approximately 10 RPM.

9. Turn metering valve stop screw counterclockwise 2-1/2 turns and tighten locknut.

10. Check installation for fuel leaks and remove shop towel from intake valley.

11. Turn engine off.

12. Remove timing meter and screened covers from intake manifold and re-install parts removed.

13. Type or print with ball point pen the dealer code and date in the space provided on the supplemental emission control label, part number 14057201 or equivalent, Figure 3 (part of kit). The label must be placed next to the existing underhood emission control information label to the extent possible. The label should not be affixed to any equipment that can be easily detached from the vehicle. Wash off the area with soap and water, dry thoroughly, and apply the new label.

PARTS INFORMATION

Part Part Number ---- ----------- 1. EGR Vacuum Control Valve 22515542 or equivalent Assembly High Altitude Application - All Models

2. Kit Contents 22516487 or equivalent

Part Quantity

Locknut Seal Metering Valve Screw Label part number 14057201 or equivalent 1 (See Figure 3)

Suggested Time

The suggested time to perform High Altitude adjustment and part replacement procedure listed above is 0.4 hour labor.

CONVERSION OF HIGH ALTITUDE VEHICLES TO LOW ALTITUDE

Dealers should advise owners moving to low altitude areas that they should purchase the service adjustment procedure outlined below which is considered an owner maintenance expense. Diesel timing should be checked or adjusted at the same approximate altitude at which the vehicle will be driven.

1. Replace the EGR vacuum control valve assembly (Figure 1) with the assembly shown in the parts information.

2. Install timing meter J-33075 or equivalent, set pump timing -4 DEG, and set idle speed to specifications.

3. Remove timing meter.

4. Type or print with ball point pen the dealer code and date in the space provided on the supplemental emission control label, part number 14055121 or equivalent (Figure 4). The label must be placed next to the existing underhood emission control information label to the extent possible. The label should not be affixed to any equipment that can be easily detached from the vehicle. Wash off the area with soap and water, dry thoroughly and apply the new label.

PARTS INFORMATION

Part Part Number ----- ----------- 1. EGR Vacuum Control Valve Assembly 22514746 or equivalent Low Altitude Application - All Models

2. Label 14055121 or equivalent (See Figure 4)

Suggested Time

The suggested time to perform the Low Altitude adjustment and part replacement procedure listed above is 0.4 hour labor.

COUNTIES WHICH ARE DESIGNAT HIGH-ALTITUDE AREAS

ARIZONA MONTANA UTAH

Apache Navajo Beaverhead Madison Beaver Morgan Cochise Yavapai Deer Lodge Meagher Box Elder Piute Coconino Gallatin Park Cache Rich Jefferson Silver Bow Carbon Salt Lake COLORADO Judith Basin Wheatland Daggett San Juan Powell Davis San Pete Adams Kit Carson Duschesne Sevier Alamosa Lake NEBRASKA Emery Summit Arapahoe LaPlata Garfield Tooele Archuleta Larimer Banner Kimball Grand Unitah Boulder Las Animas Cheyenne Sioux Iron Utah Chaffee Lincoln Juab Wasatch Cheyenne Mesa NEVADA Kane Wayne Clear Creek Mineral Millard Weber Conejos Moffat Carson City Lyon Costilla Montezuma Douglas Mineral WYOMING Crowley Montrose Elko Nye Custer Morgan Esmeralda Pershing Albany Natrona Delta Otero Eureka Storey Campbell Niobrara Denver Ouray Humboldt Washoe Carbon Park Dolores Park Lander White Pine Converse Platte Douglas Pitkin Lincoln Fremont Sublette Eagle Pueblo Goshen Sweetwater Elbert Rio Blanco NEW MEXICO Hot Springs Teton El Paso Rio Grande Johnson Vinta Fremont Routt Bernalillo Mora Laramie Washakie Garfield Saguache Catron Rio Arriba Lincoln Weston Gilpin San Juan Colfax Roosevelt Grand San Miguel Curry Sandoval Gunnison Summit DeBaca San Juan Hinsdale Teller Grant Sans Miguel Huerfano Washington Guadalupe Santa Fe Jackson Weld Harding Sierra Jefferson Hidalgo Socorro Lincoln Taos IDAHO Los Alamos Torrance Luna Union Bannock Franklin McKinley Valencia Bear Lake Fremont Otero Bingham Jefferson Blaine Lemhi OREGON Booneville Madison Butte Minidoka Harney Lake Camas Oneida Klamath Caribou Power Cassia Teton TEXAS Clark Valley Custer Jeff Davis Hudspeth Parmer

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.