1991 LEXUS SC400 brake

Troubleshooting
If the HC/CO concentration does not comply with regulations,
perform troubleshooting in the order given below.
(a) Check oxygen sensor operation.(See page FI±113)
(b) See the table below for possible cause, and then inspect
and correct the applicable causes if necessary.
 

HC 

CO 

Symptoms\
 

\
Cause
 High Normal Rough idle\
 \
1. Faulty ignitions:
   \
 \

Incorrect timing
   \
 \

Fouled, shorted or improperly gapped plugs
   \
 \

Open or crossed high±tension cords
Ckddiib\

Cracked distributor cap
Ill   \
 \
2. Incorrect valve clearance
3 L k EGR l   \
 \
3. Leaky EGR valve
4L k i k d h l   \
 \
4. Leaky intake and exhaust valves
L k li d   \
 \
5. Leaky cylinders
 High Low Rough idle\
 \
1. Vacuum leaks:
   (Fluctuating HC reading)\
 \

PCV hoses
   \
 \

EGR valve
   \
 \

Intake manifold
Ai i k h b   \
 \

Air intake chamber
Th l b d   \
 \

Throttle body
ISC l\

ISC valve
Bkb li   \
 \

Brake booster line
2L i i ifi   \
 \
2. Lean mixture causing misfire
 High High Rough idle\
 \
1. Clogged air filter g g g
(Black smoke from exhaust)\
 \
gg
2. Faulty EFI systems:   ()\
 \
yy

Faulty pressure regulator
   \
 \

yg

Clogged fuel return line
   \
 \

gg

Defective water temp. sensor
   \
 \

Defective air temp. sensor
   \
 \

Faulty ECU
   \
 \

y

Faulty injectors
\

yj

Faulty cold start injector   \
 \
yj

Faulty throttle position sensor   \
 \

Faulty air flow meter
±
ENGINE MECHANICAL Idle and/or 2,500 rpm HC/CO
Concentration Check MethodEM±29
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(b) Remove the two mounting bolts and two mounting nuts,and disconnect the throttle body from the air intake
chamber.
(c) Disconnect the following hoses, and remove the throttle body:
(1) PCV hose from throttle body
(2) Water by±pass hose from throttle body
(d) Remove the throttle body gasket.
17. DISCONNECT VACUUM HOSES Disconnect the following hoses:(1) Vacuum hose from brake booster union
(2) Vacuum hose (from VSV for heater water valve)
from air intake chamber
18. REMOVE ACCELERATOR BRACKET Remove the bolt, stud bolt and bracket.
19. REMOVE BRAKE BOOSTER UNION
Remove the union bolt, union and two gaskets.
20. REMOVE AIR INTAKE CHAMBER (a) Disconnect the following connectors:w Cold start injector connector
w VSV connector for fuel pressure control system
w (Exc. USA Spec.)
VSV connector for EGR system
(b) Remove the union bolt and two gaskets, and disconnect
the cold start injector tube from the RH delivery pipe.
±
ENGINE MECHANICAL Cylinder HeadsEM±65
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31. INSTALL ACCELERATOR BRACKETInstall the bracket with the bolt and stud bolt.
32. INSTALL BRAKE BOOSTER UNION Install the union with two new gaskets and the union bolt.
Torque: 29 N Vm (300 kgf Vcm, 22 ft Vlbf)
33. CONNECT VACUUM HOSES
Connect the following hoses:(1) Vacuum hose to brake booster union
(2) Vacuum hose (from VSV for heater water valve) to
air intake chamber
34. INSTALL THROTTLE BODY (a) Connect the following hoses:(1) Water by±pass hose to throttle body
(2) PCV hose to throttle body
(b) 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.
(c) Install the water by±pass pipe (from rear water bypass
joint) to the clamp on the engine wire cover.
(d) Connect the following connectors: (1) Throttle position sensor connector
(2) (w/ TRAC) Sub±throttle position sensor connector
(3) (w/ TRAC) Sub±throttle actuator connector
±
ENGINE MECHANICAL Cylinder HeadsEM±109
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22. DISCONNECT PS RESERVOIR TANK AND BRACKET
FROM BODY
Remove the three bolts, and disconnect the reservoir tank
and bracket assembly.
23. DISCONNECT PS PUMP FROM ENGINE Remove the three pump bolts and nut, and disconnect the PS
pump.
HINT: Put aside the PS pump, and suspend it.
24. DISCONNECT A/C COMPRESSOR (a) Disconnect the compressor connector.
(b) Remove the mounting nut, and disconnect the groundcable.
(c) Remove the mounting bolt and compressor stay.
(d) Remove the two mounting bolts, and disconnect the compressor from the engine.
HINT: Put aside the compressor, and suspend it.
25. DISCONNECT HOSES AND GROUND STRAP Disconnect the following hose and ground strap:(1) Heater water hose from water by±pass pipe
(2) Heater water hose from heater water valve
(3) Vacuum hose from brake booster union on air in-
take chamber
(4) Vacuum hose (from VSV for heater water valve)
from air intake chamber
(5) Ground strap from bracket on body
±
ENGINE MECHANICAL Cylinder BlockEM±123
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(g) Install the scuff plate.
(h) Connect the connectors.
(i) Install the lower instrument panel finish panel and glovecompartment door assembly with the four screws.
(j) Install the instrument panel under cover with the two clips.
12. INSTALL CHARCOAL CANISTER (a) Install the charcoal canister.
(b) Connect the vacuum hose and air hose to the charcoalcanister.
13. CONNECT HOSES Connect the following hose and ground strap:(1) Heater water hose to water by±pass pipe
(2) Heater water hose to heater water valve
(3) Vacuum hose to brake booster union on air intake
chamber
(4) Vacuum hose (from VSV for heater water valve) to
air intake chamber
(5) Ground strap to bracket on body
±
ENGINE MECHANICAL Cylinder BlockEM±171
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TORQUE SPECIFICATIONS
\
 \
Part tightened NVm kgf Vcm ft Vlbf
 No.1 idler pulley X Cylinder block  34 350 25
No.2 idler pulley X Cylinder block3435025 Hydraulic pump X Cylinder block 12 mm head 16 160 12  14 mm head 30 310 22
 Crankshaft pulley X Crankshaft  245 2,500 181
Camshaft timing pulley X Camshaft1081,10080 Timing belt tensioner X Oil pump  26 270 20 Spark plug X Cylinder head  18 180 13
 Drive belt tensioner X Cylinder block  16 160 12
Alternator X Alternator bracket3738027 Alternator X Cylinder block  37 380 27 Distributor housing X Cylinder head  18 185 13
 Distributor rotor X Distributor housing   3.8 39  34 in. Vlbf
Distributor cap X Camshaft timing pulley 3.839 34 in. Vlbf\
 \
RH No.2 timing belt cover X Cylinder block (for 12 mm head) 16 160 12 Drive belt idler pulley X Hydraulic pump  37 380 27
 A/C compressor X Hydraulic pump  49 500 36
A/C compressor X Cylinder block4950036 A/C compressor stay X Oil filter bracket  29 300 22 Exhaust manifold X Cylinder head  39 400 29
 Main oxygen sensor X Exhaust manifold  44 450 33
Cylinder head X Cylinder block1st3940029  2nd Turn 90 5  
 Camshaft bearing cap X Cylinder head  16 160 12
 Cylinder head cover X Cylinder head   5.9 60  52 in. Vlbf
Engine hanger X Cylinder head3738027 EGR pipe X Exhaust manifold  18 185 13 Rear water by±pass joint X Cylinder head  18 185 13
 Front water by±pass joint X Cylinder head  18 185 13
Intake manifold X Cylinder head1818513 Delivery pipe X Intake manifold  18 185 13\
 \
Fuel return pipe X RH delivery pipe(for union bolt) 35 360 26
 Fuel inlet hose X LH delivery pipe  39 400 29
for SST3334024 Cold start injector X Air intake chamber   7.8 80  69 in. Vlbf Air intake chamber X Intake manifold  18 185 13
 EGR pipe X Air intake chamber  18 185 13
EGR pipe X RH cylinder head1818513 Cold start injector tube X RH delivery pipe  15 150 11 Brake booster union X Air intake chamber  29 300 22
 Throttle body X Air intake chamber  18 185 13
ISC valve X Air intake chamber1818513 EGR valve adapter X Air intake chamber  18 185 13 EGR valve X EGR valve adapter  18 185 13
 Timing belt rear plate X Cylinder head   7.8 80  69 in. Vlbf
Water inlet housing X Water pump1818513\
 \
Catalytic converter (main) X Exhaust manifold 62 630 46\
 \
Catalytic converter (main) X Front exhaust pipe 43 440 32
\
 \
Front exhaust pipe support bracket X Transmission 43 440 32
PS pump X RH cylinder headBolt3940029  Nut 43 440 32 Main bearing cap X Cylinder block Nut 1st 27 275 20
  2nd Turn 90 5  
Bolt4950036
±
ENGINE MECHANICAL Service SpecificationsEM±181
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15. DISCONNECT HOSESDisconnect the following hoses:(1) Water by±pass hose (from water inlet housing) from ISC valve
(2) Vacuum hose (from PS air control valve) from air in-
take chamber
(3) Vacuum sensing hose (from fuel pressure regula- tor) from vacuum pipe
(4) Two vacuum hoses (from VSV for EVAP system) from vacuum pipe
(5) Vacuum hose (from charcoal canister) from vacu- um pipe
(6) Water by±pass hose (from EGR valve) from water by±pass pipe
(7) Vacuum hose (from brake booster) from air intake
chamber
(8) Vacuum hose (from VSV for heater water valve) from air intake chamber
(9) PCV hose from LH cylinder head cover
16. REMOVE AIR INTAKE CHAMBER (a) Remove the bolt, stud bolt and accelerator bracket. FI±31
EFI SYSTEM
± Fuel System (Cold Start Injector)
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(g) Install the accelerator bracket with the bolt and stud bolt.
3. CONNECT HOSES Connect the following hoses:(1) Water by±pass hose (from EGR valve) to water by±
pass pipe
(2) Vacuum hose (from brake booster) to air intake chamber
(3) Vacuum hose (from VSV for heater water valve) to
air intake chamber
(4) PCV hose to LH cylinder head cover
(5) Water by±pass hose (from water inlet housing) to ISC valve
(6) Vacuum hose (from PS air control valve) to air in- take chamber
(7) Vacuum sensing hose (from fuel pressure regula- tor) to vacuum pipe
(8) Two vacuum hoses (from VSV for EVAP system) to
vacuum pipe
(9) Vacuum hose (from charcoal canister) to vacuum pipe FI±37
EFI SYSTEM
± Fuel System (Cold Start Injector)
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