1991 LEXUS SC400 brake sensor

(l) Install the accelerator bracket with the bolt and stud bolt.
(m) Install 2 new gaskets and union with the union bolt.
Torque: 29 NVm (300 kgf Vcm, 22 ft Vlbf)
(n) Connect the following hoses:
(1) Brake booster vacuum hose to union on air intake cham-
ber
(2) Vacuum hose (from VSV for heater water valve to air in-
take chamber
29. INSTALL THROTTLE BODY
(a) Disconnect the following hoses: (1) PCV hose to throttle body
(2) Water bypass hose to throttle body
(b) Install a new gasket and throttle body with the 2 bolts and 2 nuts.
Torque: 18 N Vm (185 kgf Vcm, 13 ft Vlbf)
HINT: Use bolt 40 mm (1.57 in.) in length.
(c) Install the water bypass pipe (from the rear 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
±
1UZ±FE ENGINE ENGINE MECHANICALEG±129
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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
WhereEverybodyKnowsYourName

(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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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
WhereEverybodyKnowsYourName

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
WhereEverybodyKnowsYourName

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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