Lexus SC300 / Lexus SC400. Manual - part 612

ON–VEHICLE INSPECTION

1. 

INSPECT THROTTLE BODY
(a)  Remove the throttle body cover.

•

Remove the mounting cap nut.

•

Loosen the two bolts, and remove the throttle body
cover.

(b)  Check that the throttle linkage moves smoothly.

(c)  Check the vacuum at each port.

•

Start the engine.

•

Check the vacuum with your finger.

Port name

At idling

At 3,000 rpm

P

No vacuum

Vacuum

*E

No vacuum

Vacuum

*R

No vacuum

Vacuum

* Exc. USA Spec.
(d)  Reinstall the throttle body cover.

3. 

INSPECT AND ADJUST DASH POT (DP)

A.  Warm up engine

Allow the engine to warm up to normal operating tempera-
ture.

B.  Check idle speed

Idle speed: 700 

±

 50 rpm

C.  Remove cap, filter and separator from DP

FI–67

EFI SYSTEM   –   Air Induction System (Throttle Body)

D.  Check and adjust DP setting speed

(a)  Maintain the engine at 2,500 rpm.
(b)  Plug the VTV hole with your finger.

(c)  Release the throttle valve.
(d)  Check that the DP is set.

DP setting speed: 1,500 rpm

(e) Adjust 

the DP setting speed by turning the DP adjusting

screw.

(f) Repeat 

steps from (a) to (c), and recheck the DP setting

speed.

E. 

Reinstall separator, filter and cap to DP
HINT: Install the filter with the coarser surface facing the at-
mospheric side (outward).

F. 

Check VTV operation
(a)  Maintain the engine at 2,500 rpm.
(b)  Release the throttle valve, and check that the engine

returns to idle in a few seconds.

FI–68

EFI SYSTEM   –   Air Induction System (Throttle Body)

COMPONENTS

FI–69

EFI SYSTEM   –   Air Induction System (Throttle Body)

REMOVAL OF THROTTLE BODY

(See Components on page 

FI–69

)

1. 

DISCONNECT CABLE FROM NEGATIVE TERMINAL OF
BATTERY
CAUTION: Work must be started after approx. 20 se-
conds or longer from the time the ignition switch is
turned to the ”LOCK” position and the negative (–) termi-
nal cable is disconnected from the battery.

2. 

DRAIN ENGINE COOLANT (See page 

CO–6

)

3. 

REMOVE THROTTLE BODY COVER
(a)  Remove the mounting cap nut.
(b)  Loosen the two bolts, and remove the throttle body

cover.

4.  DISCONNECT CONTROL CABLES FROM THROTTLE

BODY
Disconnect the following cables:

(1) Accelerator 

cable

(2)  A/T throttle control cable
(3)  (w/ Cruise Control System)

Cruise control actuator cable

5. 

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

(1)  Air hose from ISC valve
(2)  Air hose (from PS air control valve) from intake air

connector

(b)  Remove the bolt holding the intake air connector to the

cylinder head cover.

(c)  Loosen the two hose clamps.
(d)  Disconnect the intake air connector from the throttle

body and air cleaner hose, and remove the intake air
connector.

FI–70

EFI SYSTEM   –   Air Induction System (Throttle Body)