1991 LEXUS SC400 brake

Troubleshooting
If the CO/HC readings do not comply with regulations, pre-
form troubleshooting in the order given below.
(a) Check oxygen sensor operation.(See page FI±73)
(b) See the table below for possible cause, and then inspect
and correct the applicable causes if necessary.
 CO HC Symptoms Cause
 Normal High Rough idle 1. Faulty ignition:
     Incorrect timing
     Fouled, shorted or improperly gapped plugs
 Open or crossed high±tension cords     Cracked distributor cap    2. Incorrect valve clearance    3. Leaky EGR valve    4. Leaky intake and exhaust valves
    5. Leaky cylinder
 Low High Rough idle 1. Vacuum leak:
   (Fluctuating HC reading)  PCV hose
     EGR valve
     Intake manifold
     Air intake chamber
 Throttle body     ISC valve     Brake booster line    2 Lean mixture causing misfire High High Rough idle 1. Clogged air filter
   (Black smoke from exhaust) 2. Faulty EFI system
     Faulty pressure regulator
     Clogged fuel return line
     Defective engine coolant temp. sensor
     Defective intake air temp. sensor
     Faulty ECU
 Fault injectors     Faulty throttle position sensor     Faulty volume air flow meter
±
ENGINE MECHANICAL Idle and/or 2,500 rpm CO/HC CheckEM±21
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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) Disconnect the following hoses:(1) Vacuum hose from brake booster union
(2) Vacuum hose (from ACIS vacuum tank)
(3) Vacuum sensing hose
(4) Air hose (from PS air control valve)
(c) Remove the two bolts, and disconnect the data link connector 1 and harness protector from the air intake
chamber.
(d) Remove the five bolts, two nuts and air intake chamber and gasket.
13. REMOVE DELIVERY PIPE AND INJECTORS (See steps 4, 5, 8 and 10 on pages FI±28 and 29)
14. REMOVE NO. 1 AND NO. 2 FUEL PIPES
15. DISCONNECT ENGINE WIRE FROM INTAKE MANIFOLD (a) Disconnect the following connectors:
(1) Engine coolant temperature sensor connector
(2) Engine coolant temperature sender gauge connec- tor
(3) Two knock sensor connectors
(4) Oil pressure switch connector
(5) Oil level sensor connector
(6) A/C compressor connector
(b) Remove the three nuts and two clamp bolts.
(c) Remove the two bolts, and disconnect the harness
protector from the intake manifold.
16. REMOVE INTAKE MANIFOLD (a) Remove the two bolts and intake manifold stay.
(b) Remove the six bolts, two nuts, intake manifold andgasket.
EM±38
±
ENGINE MECHANICAL Cylinder Head
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8. CONNECT ENGINE WIRE TO INTAKE MANIFOLD(a) Install the harness protector to the intake manifold withthe two bolts.
(b) Install the three clamp bolts and two nuts.
(c) Connect the following connectors:
(1) Engine coolant temperature sensor connector
(2) Engine coolant temperature sender gauge connec- tor
(3) Two knock sensor connectors
(4) Oil pressure switch connector
(5) Oil level sensor connector
(6) A/C compressor connector
9. INSTALL NO. 1 AND NO. 2 FUEL PIPES
Torque: 8.8 N Vm (90 kgf Vcm, 78 in. Vlbf)
10. INSTALL DELIVERY PIPE AND INJECTORS
(See steps 1, 3, 6 and 7 on pages FI±33 and 34)
Torque: 21 N Vm (210 kgf Vcm, 15 ft Vlbf)
11. INSTALL AIR INTAKE CHAMBER
(a) Install a new gasket and the intake chamber with the five
bolts and two nuts.
Torque: 21 N Vm (210 kgf Vcm, 15 ft Vlbf)
(b) Install the check connector and harness protector to the
air intake chamber with the two bolts.
(c) Connect the following hoses: (1) Vacuum hose to brake booster union
(2) Vacuum hose (to ACIS vacuum tank)
(3) Vacuum sensing hose
(4) Air hose (to PS air control valve)
±
ENGINE MECHANICAL Cylinder HeadEM±59
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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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(b) Remove the two bolts, screw and upper radiatorsupport. Remove the two upper radiator supports.
(c) Lift out the radiator with the hoses.
8. REMOVE CHARCOAL CANISTER (a) Disconnect the vacuum hose and air hose from thecharcoal canister.
(b) Remove the charcoal canister.
9. DISCONNECT PS PUMP WITHOUT DISCONNECTING HOSES
(a) Disconnect the following hoses:(1) PS air hose from No. 4 timing belt cover
(2) PS air hose from air intake chamber
(b) Remove the bolt, nut and pump rear stay.
(c) Remove the two bolts, and disconnect the PS pump from the engine.
HINT: Put aside the PS pump, and suspend it.
10. D I S C O N N E C T A / C C O M P R ESSOR WITHOUT
DISCONNECTING HOSES
(a) Disconnect the compressor connector.
(b) Remove the three mounting bolts and nut.
(c) R e m o v e t h e t h r ough bolt, and disconnect the
compressor from the engine.
HINT: Put aside the compressor, and suspend it.
11. DISCONNECT ENGINE WIRE AND HOSES (a) Disconnect the brake booster vacuum hose from theunion.
(b) Disconnect the fuel return hose from the engine oil dipstick guide clamp and No. 2 fuel pipe. Plug the hose
end.
EM±66
±
ENGINE MECHANICAL Cylinder Block
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(p) Connect the fuel return hose to the No. 2 fuel pipe andengine oil dipstick guide clamp.
(q) Connect the brake booster vacuum hose to the union.
12. INSTALL A/C COMPRESSOR (a) Install the A/C compressor with the through bolt, nut and
three bolts.
Torque: Through bolt 26 N Vm (265 kgf Vcm, 19 ft Vlbf)
Bolt and nut 52 N Vm (530 kgf Vcm, 38 ft Vlbf)
(b) Connect the A/C compressor connector.
13. INSTALL PS PUMP (a) Install the PS pump and pump rear stay with the threebolts and nut. Alternately tighten the bolts and nut.
Torque:
(A) 58 N Vm (590 kgf Vcm, 43 ft Vlbf)
(B) 39 N Vm (400 kgf Vcm, 29 ft Vlbf)
(b) Connect the following hoses:
(1) PS air hose to No. 4 timing belt cover
(2) PS air hose to air intake chamber
14. INSTALL CHARCOAL CANISTER (a) Install the charcoal canister.
(b) Connect the vacuum hose and air hose to the charcoalcanister.
15. INSTALL RADIATOR (a) Place the radiator on the body bracket.
(b) Install the upper radiator support with the two bolts andscrew. Install the two upper radiator supports.
EM±110
±
ENGINE MECHANICAL Cylinder Block
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