DIESEL ALTITUDE PERFORMANCE ADJUSTMENT PROCEDURE

The following information describes which vehicles, equipped with a 4.3L V6 diesel engine, require altitude adjustments and which are "all altitude" systems.

1982 Federal Monte Carlo models equipped with 4.3L V6 diesel engines (Engine Family C364.3D7ZZT7) will be manufactured with either high or low altitude diesel emission systems. Cars equipped with the high altitude emission 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 car was built for primary use at either high or low altitude. These procedures are considered altitude performance adjustments and apply only to in-use vehicles. They should not be used to modify vehicles prior to sale.

1982 California Monte Carlo models and 1982 Federal and California Celebrity models equipped with 4.3L V6 diesel engines (Engine Family C3G4.3D7ZZK6) were manufactured with "all altitude" diesel emission systems. Altitude perform- ance adjustments must not be used on "all altitude" vehicles.

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 following adjustment procedure. This adjustment is considered an owner maintenance expense.

1. Replace the EGR valve vacuum control assembly and vacuum modulator valve with the assemblies shown in Figure 1. Refer to Parts Information for part numbers.

2. Install magnetic tachometer probe and start engine. Allow engine to run until it reaches operating temperature. Set idle speed to specification then turn engine off.

3. Remove air crossover assembly. Install screen covers J-29657.

4. With transmission in park and A/C off, start engine.

5. Loosen locknut (Figure 2) and slowly turn metering valve stop screw clockwise until idle speed drops approximately 10 rpm.

6. Turn metering valve stop screw counterclockwise three (3) turns. Tighten locknut.

7. Check for fuel leaks around metering valve stop screw.

8. Turn engine off.

9. Remove magnetic tachometer probe and screened covers from intake manifold and reinstall parts removed.

10. Fill in dealer code and date on the supplemental emission control label, P/N 14057201 or equivalent (Figure 3). This label must be placed next to the existing underhood emission control information label. Wash off the area with soap and water, dry thoroughly, and apply the new label.

PARTS INFORMATION

Part P/N ----------------------------- --------------------- 1. EGR Valve Vacuum Control Assembly High Altitude Application 22515542 or equivalent

2. Vacuum Modulator Valve 22516009 or equivalent

3. Label 14057201 or equivalent

SUGGESTED TIME

The suggested time to perform the High Altitude Adjustment and part replacement is 0.4 hour labor.

CONVERSION OF HIGH ALTITUDE SYSTEM TO LOW ALTITUDE

Dealers should advise owners moving to low altitude areas that they should purchase the following altitude adjustment procedure. This adjustment is considered an owner maintenance expense.

1. Replace the EGR valve vacuum control assembly and vacuum modulator valve with the assemblies listed in the Parts Information section of this bulletin.

2. Fill in dealer code and date on the supplemental emission control label, P/N 14055121 or equivalent (Figure 4). The label must be placed next to the existing underhood emission control information label. Wash off the area with soap and water, dry thoroughly, and apply the next label.

PARTS INFORMATION

Part P/N --------------------------- --------------------- 1. EGR Valve Vacuum Control Assembly 22514746 or equivalent

2. Vacuum Modulator Valve 22516008 or equivalent

3. Label 14055121 or equivalent

SUGGESTED TIME

The suggested time to perform high to low altitude adjustment and part replacement is 0.2 hour labor.

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.