General information
Some models are equipped with the IAB system, which allows the air sucked into the engine to be bypassed into the combustion chamber. The intake manifold on such models is equipped with two air channels, which allows optimizing the air supply to the engine depending on the specific conditions of its operation. Maximum efficiency is achieved by actuating the switching valves depending on the current engine speed. The closed position of the valves allows achieving maximum torque at low engine speeds, while the open position serves to obtain maximum power at high speeds.
Examination
1. With the engine off, disconnect the vacuum hose from the IAB diaphragm and connect a hand vacuum pump to the latter (see accompanying illustration). If the diaphragm rod remains stationary, replace the assembly.
2. With the engine idling, check for a vacuum at the open end of the disconnected vacuum hose. The vacuum should be present at idle and disappear as the engine speed increases to 6000 rpm.
3. If there is no vacuum at idle, follow the vacuum hose from the diaphragm to the control valve located under the intake manifold and then to the vacuum reservoir. Disconnect the hose from the reservoir to the intake manifold and check for vacuum. If there is no vacuum, check the hose for cracks or signs of blockage.
4. Disconnect the IAB solenoid valve connector (see accompanying illustration). Connect the positive probe of the voltmeter to the terminal of the red-blue wire in the connector on the harness side, and the negative probe to the terminal of the black wire. When the ignition is on, there should be battery voltage. If there is no voltage, check the condition of the wiring and the quality of its contact connections.
5. If voltage is present and the vacuum lines are OK, replace the solenoid valve.
Replacement
1. To replace the diaphragm, unscrew the screws that secure it (see accompanying illustration).
2. To replace the solenoid valve assembly with the vacuum reservoir, loosen the mounting clamp (see accompanying illustration).
3. Installation is carried out in reverse order.