Lexus SC300 / Lexus SC400. Manual - part 472

2. 

INSPECT ISC VALVE OPERATION
(a)  Apply battery voltage to terminals B1 and B2, and while

repeatedly grounding S1–S2–S3–S4–S1 in sequence,
and check that the valve moves toward the closed
position.

(b)  Aplly battery voltage to terminals B1 and B2, and while

repeatedly grounding S4–S3–S2–S1–S4 in sequence,
and check that the valve moves toward the open
position.

If operation is not as specified, replace the ISC valve.

INSTALLATION OF ISC VALVE

(See Components on page 

FI–54

)

1. 

INSTALL ISC VALVE
(a)  Install a new O–ring on the throttle body.
(b)  Install the ISC valve with the two screws.

2. 

INSTALL THROTTLE BODY
(See page 

FI–45

)

–

EFI SYSTEM

Air Induction System (Idle Speed Control (ISC) Valve)

FI–55

Acoustic Control Induction System (ACIS)

ON–VEHICLE INSPECTION

INSPECT IACV

(a) Using 

a 

3–way connector, connect vacuum gauge to the

actuator hose.

(b)  Start the engine.
(c)  While the engine is idling, check that the vacuum gauge

needle does not move.

(d)  Repidly depress the accelerator pedal to fully open

position and check that the vacuum gauge needle
momentarily fluctuates approx. 53.3 kPa (400 mmHg,
15.75 in.Hg). (The actuator rod is pulled out.)

FI–56

–

EFI SYSTEM

Air Induction System (Acoustic Control Induction System (ACIS)

COMPONENTS

REMOVAL OF ACOUSTIC CONTROL
INDUCTION SYSTEM (ACIS)

1. 

DISCONNECT CABLE FROM NEGATIVE TERMINAL OF
BATTERY
CAUTION: Turn the ignition switch to ”LOCK”. Discon-
nect the cable from the negative (–) terminal of the bat-
tery. Wait at least 20 seconds before proceeding with
work.

2. (A/T)

REMOVE DIPSTICK GUIDE FOR TRANSMISSION
(a)  Remove the mounting bolt.
(b)  Pull out the dipstick guide and dipstick from the

transmission.

(c)  Remove the O–ring from the dipstic guide.

–

EFI SYSTEM

FI–57

Air Induction System (Acoustic Control Induction System (ACIS)

3. 

REMOVE VACUUM CONTROL VALVE SET
(a)  Disconnect the connector from the VSV.
(b)  Disconnect the following hoses:

(1) Vacuum hose from VSV
(2) Vacuum hose from vacuum pipe

(c)  Remove the two nuts and vacuum control valve set.

4. 

REMOVE VACUUM TANK AND VSV
Remove the screw, vacuum hose and VSV from the vacuum
tank.

5. 

REMOVE OIL DIPSTICK FOR ENGINE

6. 

DISCONNECT NO. 2 VACUUM PIPE
Remove the two nuts and disconnect the vacuum pipe.

7. 

REMOVE EGR PIPE
(a)  Loosen the union nut.
(b)  Remove the two bolts, EGR pipe and gasket.

8. 

REMOVE AIR INTAKE CHAMBER
(a)  Disconnect the following hoses:

(1) Vacuum hose from brake booster union
(2) Air hose (from charcoal canister)
(3) Vacuum hose from vacuum pipe
(4) Vacuum sensing hose
(5) Air hose (from PS air control valve)

FI–58

–

EFI SYSTEM

Air Induction System (Acoustic Control Induction System (ACIS)