GM ALTITUDE ADJUSTMENT PROGRAM-80 CADILLAC VEHICLES
The Environmental Protection Agency has approved certain adjustments on Cadillac vehicles which were built for operation at low altitudes, but are now being driven on a regular basis at 4,000 foot altitudes or higher; and also on vehicles built for high altitude operations which are now being driven on a regular basis at altitudes lower than 4,000 feet.
The approval of these adjustments is limited to vehicles now being operated at elevations other than the altitude for which the vehicles were originally designed. Procedure A is to be used for vehicles built for low altitude usage (4,000 feet or below) but now being operated mainly at altitudes higher than 4,000 feet. Procedure C is to be used for vehicles built for high altitude usage (above 4,000 feet) but now being operated mainly at altitudes of 4,000 feet or below. Refer to the attached listing of counties designated by the E.P.A. as high altitude counties.
VEHICLE INSPECTION
Vehicles designated as "LOW ALTITUDE" (Identified by FEDERAL, U.S. EPA or CALIFORNIA at bottom of underhood Vehicle Emission Control Information Label) should use Procedure A when being adjusted for high altitude operation.
Vehicles designated as "HIGH ALTITUDE" on underhood Vehicle Emission Control Information Labels should use Procedure C when being adjusted for low altitude operation.
SUPPLEMENTAL VEHICLE EMISSION CONTROL INFORMATION LABEL
When "LOW ALTITUDE" Cadillacs are adjusted for high altitude operation, supplemental label A (refer to illustration - Procedure A) must be placed next to the existing underhood Vehicle Emission Control Information Label. Wash off the area with soap and water, dry thoroughly, and apply the new label.
When vehicles identified as "HIGH ALTITUDE" are adjusted for low altitude operation, supplemental label C (refer to illustration - Procedure C) must be attached in the same manner as previously described.
DEALER AND CUSTOMER INFORMATION
ALTITUDE AND FRINGE AREA ALTITUDE DEALERSHIPS SHOULD ENCOURAGE BUYERS OF USED VEHICLES AND OWNERS WHO HAVE THEIR VEHICLES IN FOR SERVICE TO PURCHASE THIS INEXPENSIVE ADJUSTMENT SERVICE.
After performing these adjustments, dealers may advise customers that, IF THE VEHICLE IS RETURNED TO CONTINUOUS, LOW ALTITUDE OPERATION, THE ENGINE MAY BE RE-ADJUSTED TO "LOW ALTITUDE" SPECIFICATIONS PER THE CORRECT CHASSIS SERVICE MANUAL AND THE SUPPLEMENTAL VEHICLE EMISSION CONTROL INFORMATION LABEL REMOVED.
Owners of "HIGH ALTITUDE" built vehicles which are being operated mainly at altitudes lower than 4,000 feet may be encouraged to have their vehicles adjusted for low altitude driving. Should such vehicles be returned to continuous high altitude operation, owners may be advised that vehicles may be re-adjusted to high altitude specifications, per the correct Chassis Service Manual; and that the SUPPLEMENTAL VEHICLE EMISSION CONTROL INFORMATION LABEL BE REMOVED.
SPECIAL TOOLS REQUIRED
All tools or equipment required to perform these adjustments are presented in detail in Cadillac Chassis Service Manuals and include some of the following:
- A vacuum source, Mini Vac, J23738 or equivalent - An angle gage, J26701 or equivalent - Sized plug gages, J9789-02 or equivalent - Propane enrichment tool, J26911 or equivalent
ORDERING LABELS
Supplemental Vehicle Emission Control Information Labels are available from Helm Incorporated, and are being made available at no charge. Orders should be placed directly with Helm Incorporated using the following format:
PROCEDURE A
This procedure is to be used for "LOW ALTITUDE" OPEN LOOP FEDERAL or CALIFORNIA 1968-1980 Cadillac vehicles, equipped with either Cadillac or Buick (1980 model vehicles only) produced carbureted gasoline engines, when adjusting for high altitude operation.
Set choke coil one (1) notch leaner than specifications in the Chassis Service Manual (1975-1979 model vehicles only).
NOTE: Sealed chokes and chokes already set at the lean limit of the notched scale on the choke coil housing are not to be adjusted (1980 model vehicles only).
Set vacuum break(s) (if so equipped), based upon the method of measurement specified in the proper Chassis Service Manual:
Angle Gages - 2 degrees more than specified (leaner). Plug Gages - .015 more than specified (leaner).
Increase (advance) ignition timing up to 4 degrees from specifications shown on the Vehicle Emission Control Information Label.
NOTE: Timing should not be advanced if a road test reveals audible detonation.
Adjust idle mixture and idle speed to original Federal specifications as shown in the proper Chassis Service Manual and/or Vehicle Emission Control Information Label.
NOTE: Vehicles which have carburetor mixture screws covered by metal plugs are not to be mixture adjusted. On these vehicles adjust idle speeds only.
SUPPLEMENTAL VEHICLE EMISSION CONTROL INFORMATION LABEL
Supplemental label, part number 25512317, with the legend PROCEDURE A (refer to illustration below) must be installed after performing this service on a "LOW ALTITUDE" vehicle. Refer to the label installation instructions previously discussed in this bulletin.
PROCEDURE C
This procedure is to be used for Cadillacs built for "HIGH ALTITUDE", but now being operated mainly at elevations lower than 4,000 feet.
Set carburetor vacuum break(s) (if so equipped) based upon the method of measurement specified in the proper Chassis Service Manual:
Angle gages - 2 degrees less than specified (richer). Plug gages - .015 less than specified (richer).
Adjust idle mixture and idle speed to original FEDERAL or "LOW ALTITUDE" specifications as shown in the proper Chassis Service Manual.
NOTE: Vehicles which have carburetor mixture screws covered by metal plugs are not to be mixture adjusted. On these vehicles adjust idle speeds only.
SUPPLEMENTAL VEHICLE EMISSION CONTROL INFORMATION LABEL
Supplemental label, part number 25512319, with the legend PROCEDURE C (refer to illustration below) must be installed after performing this service on a "HIGH ALTITUDE" vehicle. Refer to the label installation instructions previously discussed in this bulletin.
COUNTIES WHICH ARE DESIGNATED HIGH-ALTITUDE AREAS
State of Arizona State of Idaho (CONT'D) ---------------- -------------- Apache Navajo Minidoka Teton Cochise Yavapai Oneida Valley Coconino Power
State of Colorado State of Montana ----------------- -----------------
Adams Kit Carson Beaverhead Madison Alamosa Lake Deer Lodge Meagher Arapahoe La Plata Gallatin Park Archuleta Larimer Jefferson Silver Bow Boulder Las Animas Judith Basin Wheatland Chaffee Lincoln Powell Cheyenne Mesa Clear Creek Mineral Conejos Moffat State of Nebraska Costilla Montezuma ----------------- Crowley Montrose Banner Kimball Custer Morgan Cheyenne Sioux Delta Otero Denver Ouray Dolores Park State of Nevada Douglas Pitkin ----------------- Eagle Pueblo Carson City Lyon Elbert Rio Blanco Douglas Mineral El Paso Rio Grande Elko Nye Fremont Routt Esmeralda Pershing Garfield Saguache Eureka Storey Gilpin San Juan Humboldt Washoe Grand San Miguel Lander White Pine Gunnison Summit Lincoln Hinsdale Teller Huerfano Washington Jackson Weld State of New Mexico Jefferson -------------------- Bernalillo McKinley Catron Otero State of Idaho Colfax Mora -------------- Curry Rio Arriba Bannock Cassia De Baca Roosevelt Bear Lake Clark Grant Sandoval Bingham Custer Guadalupe San Juan Blaine Franklin Harding San Miguel Bonneville Fremont Hidalgo Santa Fe Butte Jefferson Lincoln Sierra Camas Lemhi Los Alamos Socorro Caribou Madison Luna Taos
State of New Mexico (CONT'D) State of Utah (CONT'D) ---------------------------- ------------------------ Torrance Union Iron Sanpete Valencia Juab Sevier Kane Summit Millard Tooele State of Oregon Morgan Uintah Piute Utah Harney Klamath Rich Wasatch Lake Salt Lake Wayne San Juan Weber State of Texas -------------- State of Wyoming Jeff Davis Parmer ---------------- Hudspeth Albany Natrona Campbell Niobrara Carbon Park State of Utah Converse Platte -------------- Fremont Sublette Beaver Davis Goshen Sweetwater Box Elder Duchesne Hot Springs Teton Cache Emery Johnson Uinta Carbon Garfield Laramie Washakie Daggett Grand Lincoln Weston
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.
