This system, used on the four cylinder engines, uses heated air and manifold vacuum to give good driveability under varying climatic conditions.
Air can enter the air cleaner from outside the engine compartment or from the heat stove built around the exhaust manifold. A vacuum diaphragm motor, built into the air cleaner snorkel, moves the damper door, to admit hot air from the exhaust manifold, outside air, or a combination of both. Inside the air cleaner is a temperature sensor that reacts to air intake temperature and controls the amount of vacuum going to the motor.
Hesitation during warm-up may be caused by the following
- The heat stove tube disconnected.
- Vacuum diaphragm motor on the air cleaner inoperative.
- No manifold vacuum.
- Damper door does not move.
- Missing air cleaner-to-throttle body seal.
- Missing air cleaner cover seal or loose cover.
- Loose air cleaner.
- Checked for kinked, plugged or deteriorated hoses to the vacuum motor and heat stove.
- Check the condition of the gasket or seal between the air cleaner and TBI unit.
- With the air cleaner assembly installed, the damper door should be open to the outside air when the engine is not running or above 86°F (30°C).
- Start the engine. Watch the damper door in the air cleaner snorkel. When the engine is first started, the damper door should move and close off outside air.
- As the air cleaner warms up, the damper door should open slowly to the outside air.
- If the air cleaner fails to operate as described above, the vacuum motor or the temperature sensor may be defective.
- Using a vacuum pump, apply at least 7 in.Hg (23 kPa) of vacuum to the vacuum diaphragm motor. If the motor will not hold vacuum, replace the vacuum motor. If the motor holds vacuum, check motor for binding condition. Replace the temperatures sensor if the vacuum motor is working properly.