LEXUS SC400 1991 Service Repair Manual

(e) Check whether the engine rpm increases 100±300 rpmunder the following conditions:
Coolant temp.
Below 45 5C (113 5F) . . . NO increase
Above 50 5C (122 5F) . . . Increases
INSPECTION OF VSV
1. REMOVE VSV
(a) Disconnect the VSV connector.
(b) Disconnect the two vacuum hoses from VSV.
(c) Remove the bolt and VSV from the intake manifold.
2. INSPECT VSV (a) Inspect VSV for open circuit.Using an ohmmeter, check that there is continuity be-
tween the terminals.
Resistance (Cold): 33±39

If there is no continuity, replace the VSV.
(b) Inspect VSV for ground.
Using an ohmmeter, check that there is no continuity be-
tween each terminal and the body.
If there is continuity, replace the VSV.
(c) Inspect VSV operation: 1) Check that the air flows from ports E to G
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EMISSION CONTROL SYSTEMS Exhaust Gas Recirculation (EGR) SystemEC±13
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2) Apply battery voltage across the terminals
3) Check that the air flows from port E to port G
If operation is not as specified, replace the VSV.
3. REINSTALL VSV (a) Install the VSV with the nut.
Torque: 18 N Vm (185 kgf Vcm, 13 ft Vlbf)
(b) Connect the following hoses:
(1) Vacuum hose (from throttle body)
(2) Vacuum hose (from EGR vacuum modulator)
(c) Connect the VSV connector.
INSPECTION OF EGR VACUUM
MODULATOR
1. DISCONNECT VACUUM HOSES FROM EGR VACUUM MODULATOR
Disconnect the three vacuum hoses from ports P, Q and R of
the EGR vacuum modulator.
2. INSPECT EGR VACUUM MODULATOR OPERATION (a) Block ports P and R with your finger.
(b) Blow air into port Q, and check that the air passesthrough to the air filter side freely.
(c) Start the engine, and maintain speed at 2,500 rpm.
(d) Repeat the above test. Check the there is a strong resistance to air flow.
3. RECONNECT VACUUM HOSES TO EGR VACUUM MODULATOR
Connect the three vacuum hoses to the proper locations.
EC±14
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EMISSION CONTROL SYSTEMS Exhaust Gas Recirculation (EGR) System
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INSPECTION OF EGR VALVE
1. REMOVE EGR VALVE(a) Disconnect the following hoses:(1) Vacuum hose from EGR vacuum modulator
(2) Pressure hose from EGR vacuum modulator(USA Spec.)
(b) Disconnect the EGR Gas Temp. Sensor connector
(c) Loosen the nut for EGR pipe.
(d) Remove the two nuts, EGR valve and gasket.
2. INSPECT EGR VALVE Check for sticking and heavy carbon deposits.
If a problem is found, replace the EGR valve assembly.
3. REINSTALL EGR VALVE (a) Place a new gasket on the intake manifold.
(b) Install the EGR valve with the two nuts.
Torque: 18 N Vm (185 kgf Vcm, 13 ft Vlbf)
(c) Torque the nut for EGR pipe.
Torque: 64 N Vm (650 kgf Vcm, 47 ft Vlbf)
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EMISSION CONTROL SYSTEMS Exhaust Gas Recirculation (EGR) SystemEC±15
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(d) Connect the following hoses:(1) Vacuum hose from EGR vacuum modulator
(2) Pressure hose from EGR vacuum modulator(USA Spec.)
(e) Connect the EGR Gas Temp. Sensor connector.
EC±16
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EMISSION CONTROL SYSTEMS Exhaust Gas Recirculation (EGR) System
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EXHAUST GAS RECIRCULATION (EGR) SYSTEM
DESCRIPTION
To reduce NOx emission, part of the exhaust gases are recirculated through\
the EGR valve to the intake
manifold to lower the maximum combustion temperature.
OPERATION
Coolant Temp.ConditionEGR ValveExhaust Gas
Below 53 5C (127 5F)±CLOSEDNot recirculated
Above 55 5C (131 5F)(a)Idling, Deceleration, Neutral,
Low air volume, High Engine speedCLOSEDNot recirculatedAbove 55 C (131 F)
Except (a)OPEN*Recirculated
* The ECU calculates the appropriate number of steps according to the in\
take air volume and the engine speed, then
drives the stepping motor to maintain the EGR volume at a level appropri\
ate to the driving conditions.

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EMISSION CONTROL SYSTEMS Exhaust Gas Recirculation (EGR) SystemEC±15
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OPERATION (Cont'd)
EC±16±
EMISSION CONTROL SYSTEMS Exhaust Gas Recirculation (EGR) System
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INSPECTION OF EGR SYSTEM (USA
Spec.)
INSPECT SYSTEM OPERATION
(a) Using SST, connect terminals TE1 and E1 of the check(ºDIAGNOSISº) connector.
SST 09843±18020
(b) Keep the engine at 3,500 rpm.
(c) Set the transmission shift lever to the ºNº position.
(d) Remove the SST from the check connector.
SST 09843±18020
(e) Check whether the engine rpm increases 100±300 rpm under the following conditions.
Coolant temp.
Below 53 5C (127 5F) No increase
Above 55 5C (131 5F) Increases
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EMISSION CONTROL SYSTEMS Exhaust Gas Recirculation (EGR) SystemEC±17
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INSPECTION OF EGR SYSTEM
(Exc. USA Spec.)
1. CHECK AND CLEAN FILTERS IN EGR VACUUMMODULATOR
(a) Remove the cap and filter.
(b) Check the filter for contamination or damage.
(c) Using compressed air, clean the filters.
(d) Reinstall the filter and cap.
HINT: Install the filter with the coarser surface facing the at-
mospheric side (outward).
2. INSPECT SYSTEM OPERATION (a) Using SST, connect terminals TE1 and E1 of the check
(ºDIAGNOSISº) connector.
SST 09843±18020
(b) Keep the engine at 3,500 rpm.
(c) Set the transmission shift lever to the ºNº position.
(d) Remove the SST from the check connector.
SST 09843±18020
(e) Check whether the engine rpm increases 100±300 rpm under the following conditions:
Coolant temp.
Below 53 5C (127 5F) No increase
Above 55 5C (131 5F) Increases
EC±18
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EMISSION CONTROL SYSTEMS Exhaust Gas Recirculation (EGR) System
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INSPECTION OF VSV (Exc. USA Spec.)
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. REMOVE VSV (a) Disconnect the VSV connector.
(b) Disconnect the following hoses:(1) Vacuum hose (from EGR valve) from VSV
(2) Vacuum hose (from EGR vacuum modulator) from VSV
(c) Remove the bolt and VSV.
3. INSPECT VSV
A. Inspect VSV for open circuit Using an ohmmeter, check that there is continuity between
the terminals.
Resistance (Cold): 33±39

If there is no continuity, replace the VSV.
B. Inspect VSV for ground Using an ohmmeter, check that there is no continuity be-
tween each terminal and the body.
If there is continuity, replace the VSV.
C. Inspect VSV operation (a) Check that the air flows from ports E to G.
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EMISSION CONTROL SYSTEMS Exhaust Gas Recirculation (EGR) SystemEC±19
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(b) Apply battery voltage across the terminals.
(c) Check that the air flows from port E to the filter.
If operation is not as specified, replace the VSV.
4. REINSTALL VSV (a) Install the VSV with the bolt.
Torque: 18 N Vm (185 kgf Vcm, 13 ft Vlbf)
(b) Connect the following hoses:
(1) Vacuum hose (from EGR valve) to VSV
(2) Vacuum hose (from EGR vacuum modulator) to VSV
(c) Connect the VSV connector.
5. RECONNECT CABLE TO NEGATIVE TERMINAL OF BATTERY
INSPECTION OF EGR VACUUM
MODULATOR (Exc. USA Spec.)
1. DISCONNECT VACUUM HOSES FROM EGR VACUUMMODULATOR
Disconnect the three vacuum hoses from ports P, Q and R of
the EGR vacuum modulator.
2. INSPECT EGR VACUUM MODULATOR OPERATION (a) Block ports P and R with your finger.
(b) Blow air into port Q, and check that the air passesthrough to the air filter side freely.
(c) Start the engine, and maintain speed at 2,500 rpm.
(d) Repeat the above test. Check that there is a strong resistance to air flow.
3. RECONNECT VACUUM HOSES TO EGR VACUUM MODULATOR
Connect the three vacuum hoses to the proper locations.
EC±20
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EMISSION CONTROL SYSTEMS Exhaust Gas Recirculation (EGR) System
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