1991 LEXUS SC400 engine

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 enginereturns to idle in a few seconds.
FI±68
EFI SYSTEM
± Air Induction System (Throttle Body)
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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 ºLOCKº 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 bodycover.
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)
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INSTALLATION OF THROTTLE BODY
(See Components o page FI±69)
1. INSTALL THROTTLE BODY (a) Install the two water by±pass hoses and pipe to thethrottle body.
(b) Connect the following hoses: (1) PCV hose to throttle body
(2) Water by±pass hose to throttle body
(c) Install a new gasket and throttle body with the two bolts and two nuts.
Torque: 18 N Vm (185 kgf Vcm, 13 ft Vlbf)
HINT: Use bolts 40 mm (1.57 in.) in length.
(d) Install the water by±pass pipe (from rear water by±pass
joint) to the clamp on the engine wire cover.
(e) Connect the following hoses: (1) Water by±pass hose to the ISC valve
(2) (USA Spec.) Vacuum hose to throttle body
(3) (Exc. USA Spec.) Three vacuum hoses to throttle body FI±77
EFI SYSTEM
± Air Induction System (Throttle Body)
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(d) Connect the following hoses:(1) Air hose to ISC valve
(2) Air hose (from PS air control valve) to intake air con-
nector
4. CONNECT CONTROL CABLES TO THROTTLE BODY Connect the following cables:(1) Accelerator cable
(2) A/T throttle control cable
(3) (w/ Cruise Control System) Cruise control actuator cable
5. INSTALL THROTTLE BODY COVER Install the throttle body cover and hose clamp with the two
bolts and cap nut.
6. CONNECT CABLE TO NEGATIVE TERMINAL OF BATTERY
7. FILL WITH ENGINE COOLANT (See page CO±7)FI±79
EFI SYSTEM
± Air Induction System (Throttle Body)
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Idle Speed Control (ISC) Valve
ON±VEHICLE INSPECTION
INSPECT ISC VALVE FOR OPERATING SOUNDCheck that there is a clicking sound immediately after stop-
ping the engine.
If the rpm operation is not as specified, check the ISC valve,
wiring and ECU.
FI±80
± Air Induction System (Idle Speed Control (ISC\
) Valve)EFI SYSTEM
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EFI Main Relay
INSPECTION OF EFI MAIN RELAY
1. REMOVE EFI MAIN RELAY FROM RELAY BOX IN ENGINE
COMPARTMENT
2. INSPECT EFI MAIN RELAY
A. Inspect relay continuity (a) Using an ohmmeter, check that there is continuity
between terminals 1 and 3.
(b) Check that there is no continuity between terminals 2 and 4.
If continuity is not as specified, replace the relay.
B. Inspect relay operation (a) Apply battery voltage across terminals 1 and 3.
(b) Using an ohmmeter, check that there is continuity
between terminals 2 and 4.
If operation is not as specified, replace the relay.
3. REINSTALL EFI MAIN RELAY FI±85
± Electronic Control System (EFI Main Relay\
)EFI SYSTEM
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Ignition Main Relay
INSPECTION OF IGNITION MAIN RELAY
1. REMOVE IGNITION MAIN RELAY FROM RELAY BOX INENGINE COMPARTMENT
2. INSPECT IGNITION MAIN RELAY
A. Inspect relay continuity (a) Using an ohmmeter, check that there is continuity
between terminals 3 and 6.
(b) Check that there is continuity between terminals 4 and 5.
(c) Check that there is no continuity between terminals 1 and 2.
If continuity is not as specified, replace the relay.
B. Inspect relay operation (a) Apply battery voltage across terminals 3 and 6.
(b) Using an ohmmeter, check that there is continuitybetween terminals 1 and 2.
(c) Apply battery voltage across terminals 4 and 5.
(d) Check that there is continuity between terminals 1 and 2.
If operation is not as specified, replace the relay.
3. REINSTALL IGNITION MAIN RELAY
FI±86
± Electronic Control System (Igniti\
on Main Relay)EFI SYSTEM
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INSPECTION OF EGR GAS
TEMPERATURE SENSOR
1. DISCONNECT CABLE FROM NEGATIVE TERMINAL OFBATTERY
CAUTION: Work must be started after approx. 20 se-
conds or longer from the time the ignition switch is
turned to the ºLOCKº position and the negative (±) termi-
nal cable is disconnected from the battery.
2. DRAIN ENGINE COOLANT
3. REMOVE EGR VALVE (a) Disconnect the EGR gas temperature sensor.
(b) Disconnect the following hoses from the EGR valve:(1) Water by±pass hose (from ISC valve)
(2) Water by±pass hose (from rear water by±pass joint)
(c) Remove the two nuts, EGR valve and gasket.
4. REMOVE EGR VALVE ADAPTOR (a) Disconnect the EGR gas temperature sensor.
(b) Disconnect the PCV hose from the EGR valve adaptor.
(c) Remove the two bolts, two nuts, EGR valve adaptor andgasket. FI±103
EFI SYSTEM
± Electronic Control System (EGR Gas Temperature Sensor (USA Spec. only))
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