Lexus SC300 / Lexus SC400. Manual — part 342
3.
INSPECT EGR VALVE
Check for sticking and heavy carbon deposits.
If a problem is found, replace the EGR valve assembly.
4.
REINSTALL EGR VALVE
(a) Place a new gasket on the EGR valve adaptor.
NOTICE:
•
Do not touch the adaptor and EGR valve surfaces of the
gasket with your hand.
•
Align the port holes of the gasket and adaptor.
Be careful of the installation direction.
(b) Install the EGR valve with the two nuts.
Torque: 18 N
⋅
m (185 kgf
⋅
cm, 13 ft
⋅
lbf)
(c) Install the vacuum modulator bracket to the EGR valve.
(d) Connect the following hoses:
(1) Vacuum hose (from VSV) to EGR valve
(2) Vacuum hose (from VSV) to EGR vacuum modula-
tor
(3) Vacuum hose (from EGR vacuum modulator) to
EGR valve
(4) Water by–pass hose (from ISC valve) to the EGR
valve
(5) Water by–pass hose (from rear water by–pass
joint) to the EGR valve
5.
REFILL WITH ENGINE COOLANT (See page
–
EMISSION CONTROL SYSTEMS
Exhaust Gas Recirculation (EGR) System
EC–25
THREE–WAY CATALYST (TWC) SYSTEM
DESCRIPTION
To reduce HC, CO and NOx emissions, they are oxidized, reduced and converted to nitrogen (N), carbon diox-
ide (CO) and water (HO) by the catalyst.
OPERATION
INSPECTION OF EXHAUST PIPE
ASSEMBLY
1. CHECK CONNECTIONS FOR LOOSENSESS OR
DAMAGE
2. CHECK
CLAMPS
FOR
WEAKNESS,
CRACKS OR
DAMAGE
INSPECTION OF CATALYTIC
CONVERTER
CHECK FOR DENTS OR DAMAGE
If any part of the protector is damaged or dented to the extent
that is contacts the catalyst, repair or replace it.
INSPECTION OF HEAT INSULATOR
1.
CHECK HEAT INSULATOR FOR DAMAGE
2. CHECK
FOR
ADEQUATE
CLEARANCE
BETWEEN
CATALYTIC CONVERTER AND HEAR INSULATOR
–
EMISSION CONTROL SYSTEMS
Three–way Catalyst (TWC) System
EC–17
COMPONENTS
REPLACEMENT OF CATALYTIC
CONVERTERS
(Front Catalytic Converter)
1.
REMOVE CATALYTIC CONVERTER (FRONT)
(a) Check that the converter is cool.
(b) Remove the two bolts and nuts holding the catalytic
converters to the front exhaust pipe.
(c) Disconnect the front exhaust pipe from the catalytic
converter, and remove the gasket.
(d) Remove the four nuts holding the catalytic converter to
the exhaust manifold.
2. REINSTALL
CATALYTIC
CONVERTER
(a) Install a new gasket and the catalytic converter to the
exhaust manifold with four new nuts.
Torque: 62 N
⋅
m (630 kgf
⋅
cm, 46 ft
⋅
lbf)
(b) Install a new gasket to front end of the front exhaust
pipe, and torque the front exhaust pipe to the catalytic
converter.
Torque: 43 N
⋅
m (440 kgf
⋅
cm, 32 ft
⋅
lbf)
EC–18
–
EMISSION CONTROL SYSTEMS
Three–way Catalyst (TWC) System
(Rear Catalytic Converter)
1. (USA
Spec.)
REMOVE SUB–OXYGEN SENSOR
Remove the two nuts and sub–oxygen sensor from the front
exhaust pipe.
2.
REMOVE REAR CATALYTIC CONVERTER (FRONT
EXHAUST PIPE)
(a) Remove the two bolts and nuts holding the front exhaust
pipe to the center exhaust pipe.
(b) Remove the two bolts and nuts holding the front exhaust
pipe to the front catalytic converter, and remove the front
exhaust pipe and two gaskets.
3. REINSTALL REAR CATALYTIC CONVERTER (FRONT
EXHAUST PIPE)
Install the two new gaskets, the front exhaust pipe with the
four bolts and new nuts.
Torque: 43 N
⋅
m (440 kgf
⋅
cm, 32 ft
⋅
lbf)
4. (USA
Spec.)
REINSTALL SUB–OXYGEN SENSOR
Install the new gasket, the sub–oxygen sensor to the front ex-
haust pipe with the two nuts.
Torque: 18 N
⋅
m (180 kgf
⋅
cm, 13 ft
⋅
lbf)
–
EMISSION CONTROL SYSTEMS
Three–way Catalyst (TWC) System
EC–19
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