The intake manifold is divided into two paths of different lengths and diameters: long path (for low power) 650 mm long and 36 mm in diameter and a short path (for high power) 370 mm long and 45 mm in diameter.
A vacuum diaphragm assembly is installed at each end of the casing. Each diaphragm is connected to the axis of the throttle valve through a pusher. The vacuum diaphragms are connected to an electrically controlled solenoid valve, which in turn is connected to the brake vacuum pump. The pump is installed on the end face of the cylinder head.
At engine speeds below 1800 rpm and above 5080 rpm, the ECU closes the solenoid valve, removing the vacuum from the diaphragms, and the throttle valves close. With valves, the short air supply paths are closed and the air flow enters through the long path.
At engine speeds between 1800 rpm and 5080 rpm, the ECU opens the solenoid valve. The vacuum acts on the vacuum diaphragms and opens the four throttle valves. With the valves open, the incoming air flows through both short and long paths for maximum power.
Examination
1. To test the system, start the engine at idle. Slowly increase engine speed and observe vacuum diaphragm lifters. At approximately 1800 rpm, the pushrods should act on the diaphragms.
2. To check the operation of the solenoid valve, remove the vacuum tube from the diaphragm. Run the engine to idle. Place your finger on the end of the pipe; there must be no vacuum in the pipe. When the engine speed is slowly increased to 1800 rpm, a vacuum should be felt in the pipe.
ACAV valve block
Removing
1. Remove intake manifold.
2. Remove fuel line.
3. Remove the vacuum hoses from the fuel pressure regulator and the ACAV diaphragm hose from the tee.
4. Unscrew the three bolts securing the valve block to the cylinder head and remove it together with the gasket.
5. Check that the throttle valves open freely and easily.
Vacuum diaphragm
ACAV Vacuum Diaphragm Unit
Removing
1. Remove the vacuum hose from the diaphragm housing.
2. Unscrew the two bolts securing the block with the vacuum diaphragm to the valve block, and remove the block.
Solenoid valve
1 – a nut of fastening of the electromagnetic valve,
2 - electrical wiring connector,
3 - hose connection
The electromagnetic control valve is installed on the left end of the cylinder head.
Removing
1. Release bracket and remove electrical connector.
2. Unscrew the valve fastening nut, remove the valve and remove the vacuum hoses from the valve.