Disconnect 3 hoses from top of HAC valve. Blow air into each hose. Check that air flows into carburetor. Reconnect hoses.
Remove check valve. Check that air flows from White pipe to Black pipe, but not in other direction.
Remove distributor cap and rotor. Apply vacuum to diaphragms. Check that vacuum advancer moves in accordance with applied vacuum. Reinstall the rotor and distributor cap. Start engine and warm to normal operating temperature.
If at high altitude, disconnect and plug hose at distributor sub-diaphragm. Ignition timing should be 7° BTDC. Reconnect hose. Timing should advance to 13° BTDC.
Disconnect and plug hose from Black side of check valve. Timing should not change for at least 1 minute. Stop engine and reconnect hose.
If at low altitude, ignition timing should be 7° BTDC. Disconnect and plug hose at lower port of HAC valve. Timing should advance to 13° BTDC.
Disconnect and plug hose from Black side of check valve. Timing should not change for at least 1 minute. Stop engine and reconnect hoses.

Fig 1: Land Cruiser High Altitude Compensation System

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Land Cruiser