Acoustic Control Induction System (ACIS) — description and component replacement
Description
1. The PCM-controlled Acoustic ControlInduction System (ACIS) varies the effective length of the intake manifold runners in response to engine speed and the angle of the throttle plate inside the throttle body. This capability increases efficiency and power at low and high speeds.
2. The ACIS consists of a PCM-controlledVacuum Switching Valve (VSV), an actuator, a vacuum tank and an intake air control valve. The VSV controls the intake vacuum applied to the actuator. The actuator is a vacuum diaphragm that uses a pushrod and bell crank to open and close the intake air control valve (see illustration). The vacuum tank, bell crank and pushrod are an integral part of the intake manifold. The vacuum tank is used to maintain a constant source of vacuum to keep the intake air control valve closed during deceleration (low vacuum). The intake air control valve, which is also an integral part of the intake manifold (see illustration), opens and closes to alter the effective length of the intake manifold runners in two stages. There is one large intake air control valve for all four intake runners.
i.2a ACIS actuator bell-crank (integral with intake manifold)
i.2b Identifying the ACIS vacuum tank (A) and intake air control valve (B) inside of the intake manifold
3. At low-to-medium speeds, the PCM activates the VSV, sending vacuum to the actuator diaphragm. The actuator closes the intake air control valve, increasing the length of the intake manifold and improving intake efficiency.
4. At higher speeds, the PCM deactivatesthe VSV, cutting vacuum to the actuator diaphragm. The actuator opens the intake air control valve, decreasing the length of the intake manifold and improving engine power.
VSV replacement
Note: The vacuum tank/bell crank and the intake air control valve are integral components of the intake manifold. If these particular components fail, replace the intake manifold (see Engine). For the replacement of the IAC valve actuator, see Intake air control valve actuator — replacement.
Note: The VSV is located at the top end of the intake manifold (passenger’s side)
5. Remove the engine cover.
6. Locate the VSV (see illustration).
15. 6 Identifying the Acoustic Control Induction System Vacuum Switching Valve (ACTS VSV)
7. Disconnect the electrical connector fromthe VSV.
8. Clearly label the vacuum hoses, thendisconnect both hoses from the VSV.
9. Remove the VSV mounting bolt andremove the VSV.
10. Installation is the reverse of removal.