LEXUS SC400 1991 Service Repair Manual

INSPECTION OF PCV VALVE
1. REMOVE PCV VALVE(a) Disconnect the PCV hose from the PCV valve.
(b) Remove the PCV valve.
2. INSTALL CLEAN HOSE TO PCV VALVE
3. INSPECT PCV VALVE OPERATION (a) Blow air into the cylinder head side, and check that airpasses through easily.
CAUTION: Do not suck air through the valve. Petroleum
substances inside the valve are harmful.
(b) Blow air into the air intake chamber side, and check that air passes through with difficulty.
If operation is not as specified, replace the PCV valve.
4. REMOVE CLEAN HOSE FROM PCV VALVE
5. REINSTALL PCV VALVE
INSPECTION OF PCV HOSE AND
CONNECTIONS
VISUALLY INSPECT HOSE, CONNECTIONS AND GASKETS Check for cracks, leaks or damage.
±
EMISSION CONTROL SYSTEMS Positive Crankcase Ventilation (PVC) SystemEC±7
WhereEverybodyKnowsYourName

FUEL EVAPORATIVE EMISSION CONTROL (EVAP) SYSTEM
DESCRIPTION
To reduce HC emission, evaporated fuel from the fuel tank is routed throug\
h the charcoal canister to the
intake manifold for combustion in the cylinders.
OPERATION
CoolantVSVThrottle ValveCanister Check ValveCheck
Valve inEvaporated F el (HC)Coolant
Te m p .VSVThrottle Valve
Opening(1)(2)(3)Valve inCapEvaporated Fuel (HC)
BelowNoFulley closedBelow
40 5C (104 5F)
No
OperationFulley closed.±±±±Small volume of HC from
Fully closed or
bellow Specified air
canister enters air intake
chamber.
Above
bellow Specified air
volume.±±±±chamber.
Above
40 5C (104 5F)Operation
Conditions other
than above.±±±±
HC from canister enters air
intake chamber in the amout
programmed in accordance
with the intake air volume.
High pres-
sure in tank±±±OPENCLOSEDCLOSEDHC from tank is absorbed
into the canister.
High vacuum
in tank±±±CLOSEDOPENOPENAir is led into the fuel tank.
INSPECTION OF FUEL VAPOR LINES,
FUEL TANK AND TANK CAP
1. VISUALLY INSPECT LINES AND CONNECTIONS
Look for loose connections, sharp bends or damage.
2. VISUALLY INSPECT FUEL TANK Look for deformation, cracks or fuel leakage.
EC±8
±
EMISSION CONTROL SYSTEMS Fuel Evaporative Emission Control (EVAP) System
WhereEverybodyKnowsYourName

3. VISUALLY INSPECT FUEL TANK CAPCheck if the cap and/or gasket are deformed or damaged.
If necessary, repair or replace the cap.
INSPECTION OF CHARCOAL CANISTER
1. REMOVE CHARCOAL CANISTER(a) Disconnect the following hoses:(1) Vacuum hose (from VSV) from charcoal canister
(2) EVAP hose from charcoal canister
(b) Disconnect the grommet on the check valve from the bracket, and remove the charcoal canister.
(c) Remove the check valve from the hose end on the charcoal canister.
2. VISUALLY INSPECT CHARCOAL CANISTER Look for cracks or damage.
3. CHECK FOR CLOGGED FILTER AND STUCK CHECK VA LV E
(a) Using low pressure compressed air, blow into port A and
check that air flows without resistance from the other
ports.
(b) Blow into port B and check that air does not flow from the
other ports.
If a problem is found, replace the charcoal canister.
±
EMISSION CONTROL SYSTEMS Fuel Evaporative Emission Control (EVAP) SystemEC±9
WhereEverybodyKnowsYourName

4. CLEAN FILTER IN CANISTERClean the filter by blowing 294 kPa (3 kgf/cm2, 43 psi) of com-
pressed air into port A while holding port B closed.
NOTICE:
w Do not attempt to wash the canister.
w No activated carbon should come out.
5. REINSTALL CHARCOAL CANISTER
HINT: Install the check valve with black port facing the char-
coal canister side.
(a) Install the check valve to the hose end on the charcoalcanister.
(b) Install the charcoal canister.
(c) Install the grommet on the check valve to the bracket.
(d) Connect the following hoses: (1) Vacuum hose (from VSV) to charcoal canister
(2) EVAP hose to charcoal canister
COMPONENTS FOR REMOVAL AND INSTALLATION OF VSV
EC±10±
EMISSION CONTROL SYSTEMS Fuel Evaporative Emission Control (EVAP) System
WhereEverybodyKnowsYourName

INSPECTION OF VSV
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 INTAKE AIR CONNECTOR (a) Disconnect the following hoses:(1) Air hose (from ISC valve) from intake air connector
(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.
3. REMOVE VSV (a) Disconnect the VSV connector.
(b) Disconnect the following hoses:(1) Vacuum hose (from vacuum pipe) from VSV
(2) Vacuum hose (from charcoal canister) from VSV
(c) Remove the two bolts and VSV from the cylinder head.
(d) Disconnect the two wire clamps from the VSV bracket, and remove the VSV.
±
EMISSION CONTROL SYSTEMS Fuel Evaporative Emission Control (EVAP) SystemEC±11
WhereEverybodyKnowsYourName

4. INSPECT VSV
A. Inspect VSV for open circuitUsing an ohmmeter, check that there is continuity between
the terminals.
Resistance (Cold): 30±34

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 with difficulty from ports E to F.
(b) Apply battery voltage across the terminals.
(c) Check that the air flows without resistance from port Eto F.
If operation is not as specified, replace the VSV.
5. REINSTALL VSV (a) Install the VSV with the two bolts.
(b) Connect the two wire clamps to the VSV bracket.
EC±12
±
EMISSION CONTROL SYSTEMS Fuel Evaporative Emission Control (EVAP) System
WhereEverybodyKnowsYourName

(c) Connect the following hoses:(1) Vacuum hose (from vacuum pipe) to VSV
(2) Vacuum hose (from charcoal canister) to VSV
(d) Connect the VSV connector.
6. REINSTALL INTAKE AIR CONNECTOR (a) Connect the end portions of the intake air connector tothe throttle body and air cleaner hose.
(b) Tighten the two hose clamps.
(c) Install the bolt holding the intake air connector to the cylinder head cover.
(d) Connect the following hoses: (1) Air hose (from ISC valve) to intake air connector
(2) Air hose (from PS air control valve) to intake air con-
nector
7. RECONNECT CABLE TO NEGATIVE TERMINAL OF BATTERY
INSPECTION OF CHECK VALVE
1. REMOVE CHECK VALVE(a) Disconnect the grommet on the check valve from thebracket.
(b) Remove the check valve from the hose end on the charcoal canister.
(c) Remove the grommet from the check valve.
2. INSPECT CHECK VALVE (a) Check that air flows from the yellow port to the blackport.
(b) Check that air does not flow from the black port to the yellow port.
If operation is not as specified, replace the check valve.
±
EMISSION CONTROL SYSTEMS Fuel Evaporative Emission Control (EVAP) SystemEC±13
WhereEverybodyKnowsYourName

3. REINSTALL CHECK VALVEHINT: Reinstall the check valve with the black port facing the
charcoal canister side.
(a) Install the grommet to the check valve.
(b) Install the check valve to the hose end on the charcoalcanister.
(c) Install the grommet on the check valve to the bracket.
EC±14
±
EMISSION CONTROL SYSTEMS Fuel Evaporative Emission Control (EVAP) System
WhereEverybodyKnowsYourName

EXHAUST GAS RECIRCULATION (EGR) SYSTEM
DESCRIPTION
To reduce NOx emission, part of the exhaust gases are recirculated through\
the EGR valve to the intake man-
ifold to lower the maximum combustion temperature.
OPERATION
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.
Coolant
Temp.VSVThrottle Valve OpeningPressure in the EGR Valve Pressure ChamberEGR VacuumModulatorEGR
ValveExhaust Gas
Below 45
COPENCLOSEDNot recircu-
(113
F)OPEN±±±CLOSEDlated
Positioned be-
low EGR port±±CLOSEDNot recircula- ted
Above 50 5C
(122 5F)CLOSEDPositioned be-
tween EGRport
(1)
LOW* Pressure constantly
alternating between
OPENS passage to atmosphereCLOSEDNot recircula- ted
tween EGR port
and R port(2)
HIGHalternating between
low and highOPENS passage
to atmosphereOPENRecirculated
Above 50 5C
(122 5F)CLOSEDPositioned
above R port(3)
HIGH**CLOSES passage to atmosphereOPENRecirculated(increase)
* Pressure increases Modulator closes EGR valve opens Pressure drops EGR Valve closes Modulator opens
** When the throttle valve is positioned above the R port, the EGR vacuum m\
odulator will close the atmosphere passage and
open the EGR valve to increase the EGR gas, even if the exhaust pressure\
is insufficiently low.
±
EMISSION CONTROL SYSTEMS Exhaust Gas Recirculation (EGR) SystemEC±11
WhereEverybodyKnowsYourName

INSPECTION OF EGR SYSTEM
1. CHECK AND CLEAN FILTER IN EGR VACUUMMODULATOR
(a) Remove the cap and filter.
(b) Check the filter for contamination or damage.
(c) Using compressed air, clean the filter.
(d) Reinstall the filter and cap.
HINT: Install the filter with the coarser surface facing the at-
mospheric side (out ward).
2. INSPECT SYSTEM OPERATION (a) Connect the tachometer to terminal IG ± of the check(ºDIAGNOSISº) connector.
(b) Using SST connect the terminals TE1 and E1 of the check (ºDIAGNOSISº) connector.
SST 09843±18020
(c) Keep the engine at 3,500 rpm with the transmission in ºNº position.
(d) Remove the SST from the check connector.
SST 09843±18020
EC±12
±
EMISSION CONTROL SYSTEMS Exhaust Gas Recirculation (EGR) System
WhereEverybodyKnowsYourName