This system is only found on the Premier models.
See Figure 1
The Thermostatically-controlled Air Cleaner (TAC) system provides heated air to the throttle body during the engine warm-up.
The TAC system is comprised of a heat stove that wraps around the exhaust manifold, a heated air tube, an air temperature sensor, and a vacuum motor operated air valve.
The air valve in the air cleaner blends air warmed from the heat stove on the air cleaner with ambient (outside) air. The air valve can close the opening to either air source or blend a mixture of both depending upon operating conditions.
The valve in the air cleaner closes off the preheated air opening when vacuum is not applied to the valve vacuum motor. When the engine is started, the air temperature in the air cleaner is monitored by the temperature sensor. The air temperature sensor is located in the cleaner cover. If the intake charge temperature is below the calibrated opening point of the sensor, vacuum will be applied to the air valve vacuum motor to move the air valve toward the ambient air opening. Only warmed air from the heat stove on the exhaust manifold will enter the air cleaner. As the exhaust manifold warms up and the temperature of the air entering the throttle body bonnet from the heat stove rises, the air temperature sensor begins to open and vacuum is bled off. This causes the air opening toward the heat stove air opening. In this way, ambient air and heated air from the heat stove are mixed for optimum engine performance and emission control.
Air Valve Vacuum Motor
- With the engine not operating, observe the ambient air inlet duct at the air cleaner and observe the position of the air valve. The air valve should be fully open to incoming ambient air (heat OFF position).
- Start the engine and observe the position of the air valve. It should be fully closed to incoming ambient air (heat ON position) below approximately 70°F (21°C).
- Depress the throttle rapidly ( 1 / 2 - 3 / 4 position) and release. The air valve should briefly remain stationary, then move toward the heat OFF position and then back to the heat ON position.
- Warm the engine to normal operating temperature. Observe the ambient air duct and air valve, which should be fully open to ambient air above 70°F (21°C).
- Stop the engine.
- If the air valve did not function as described in the previous test, inspect for a mechanical bind in the snorkel or disconnected or leaking vacuum hoses. Also check for vacuum leaks at the vacuum motor, air temperature sensor or intake manifold.
- If the air valve can be manually operated (it should not stick, but move freely) and the hoses are not leaking or disconnected, connect a vacuum hose from an intake manifold vacuum source directly to the vacuum motor and start the engine.
- If the air valve closes, the air temperature sensor is defective and must be replaced with a new one. If the air valve does not close, replace the vacuum motor with a new one.
- Disconnect the vacuum hoses from the air temperature sensor located on the air cleaner cover.
- Connect a hand-operated vacuum pump to the vacuum source side of the sensor and a vacuum gauge to the vacuum motor side of the sensor.
- Apply 16 in. Hg (47 kPa) vacuum to the sensor.
- With the sensor at temperature below 50°F (10°C), vacuum should be maintained.
- Warm the sensor to above 70°F (21°C). The vacuum should not be maintained by the sensor.
- Replace the sensor with a new one if the sensor does not perform as described.
REMOVAL & INSTALLATION
Air Valve Vacuum Motor
- Remove the air cleaner.
- Disconnect the vacuum hose from the air valve motor.
- Remove the rivet holding the air valve vacuum motor.
- Lift the motor, tilt it to one side to disconnect the motor linkage from the air valve assembly and remove the motor.
- Insert the replacement vacuum motor linkage into the air valve assembly and position it in the snorkel.
- Attach the motor to the snorkel with a rivet. Ensure that the rivet does not interfere with the movement of the air valve.
- Connect the vacuum hose. Install the air cleaner assembly and test for proper operation of the TAC system.
- The air temperature sensor is located in the air cleaner cover.
- Mark the air temperature sensor vacuum tubes for installation reference. Remove the vacuum tubes from the air temperature sensor.
- Remove the air cleaner cover.
- Remove the air temperature sensor retaining clips.
- Remove the sensor.
- Install the air temperature sensor in air cleaner cover. Secure with the retaining clips.
- Install the air cleaner cover onto the air cleaner.
- Connect the vacuum tubes to the air temperature sensor.