1991 LEXUS SC400 fuel pressure

Troubleshooting
If the CO/HC concentration does not comply with regulations,
perform troubleshooting in the order given below.
(a) Check main heated oxygen sensor operation.
(See MFI System on page EG±400)
(b) See the table below for possible causes, and then inspect and correct the applicable causes if necessary.
 CO HC Problems\
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Causes
 Normal High Rough idle\
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1. Faulty ignitions: 


 


 


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Incorrect timing
   \
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Fouled, shorted or improperly gapped plugs
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Open or crossed high±tension cords
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Cracked distributor cap
   \
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2. Incorrect valve clearance   \
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3. Leaky EGR valve 


 


 


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4. Leaky intake and exhaust valves
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5. Leaky cylinder
 Low High Rough idle\
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1. Vacuum leaks:
   (Fluctuating HC reading)\
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PCV hose
   \
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EGR valve 


 


 


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Intake manifold
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Throttle body
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IAC valve
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Brake booster line
   \
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2. Lean mixture causing misfire 

High 

High 

Rough idle\
 

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1. Restricted air filter
   (Black smoke from exhaust)\
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2. Faulty MFI systems:
   \
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Faulty pressure regulator
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Clogged fuel return line
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Defective ECT switch   \
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Faulty ECM 


 


 


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Faulty injector
   \
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Faulty throttle position sensor
   \
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Faulty volume air flow meter
V02130
EG±36±
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COMPRESSION CHECK
EG21U±02
HINT: If there is lack of power, excessive oil consumption or
poor fuel economy, measure the compression pressure.
1. WARM UP AND STOP ENGINE Allow the engine to warm up to normal operating tempera-
ture.
2. DISCONNECT NEGATIVE TERMINAL CABLE FROM BATTERY
CAUTION: Work must be started after 90 seconds from
the time the ignition switch is turned to the ªLOCKº posi-
tion and the negative (±) terminal cable is disconnected
from the battery.
3. REMOVE INTAKE AIR CONNECTOR
(a) Disconnect the following hoses: (1) Air hose from IAC valve
(2) Air hose (from air control valve on PS pump) from intake
air connector
(b) Remove the bolt holding the intake air connector to the cylinder head cover.
(c) Remove the 2 hose clamps.
(d) Disconnect the intake air connector from the throttle body
and air cleaner hose, and remove the intake air connector.
4. REMOVE UPPER HIGH±TENSION CORD COVER
(a) Remove the 2 bolts.
(b) Disconnect the front side claw groove of the upper cord cover
from the claw of lower cord cover, and remove the upper cord
cover.
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24. REINSTALL RH ENGINE WIRE COVER
(a) Fit portions A and B of the engine wire cover, matching themwith the lower high±tension cord cover and No.3 timing belt
cover.
(b) Install the timing belt cover with the bolt.
25. REINSTALL LH ENGINE WIRE COVER
(a) Connect portions A and B of the engine wire cover to the wire
brackets.
(b) Set the VSV (for the fuel pressure) wire in original position.
(c) Fit portions C and D of the engine wire cover, matching them with the lower high±tension cord cover and No.3 timing belt
cover.
(d) Install the timing belt cover with the 2 bolts.
26. REINSTALL UPPER HIGH±TENSION CORD COVER
(a) Fit portion A of the upper high±tension cord cover matching the top of the lower high±tension cord cover.
(b) Push the front side of the upper high±tension cord cover, and
fit the front side claw groove of the upper high±tension cord
cover to the claw of the lower high ±tension cord cover.
(c) Install the upper high±tension cord cover with the 2 bolts.
27. REINSTALL INTAKE AIR CONNECTOR
(a) Connect the end portions of the intake air connector to the throttle body and air cleaner hose.
(b) Tighten the 2 hose clamps.
(c) Install the bolt holding the intake air connector to the cylinder head cover.
EG±42
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30. INSTALL VSV FOR EVAP SYSTEMInstall the VSV with the 2 bolts.
31. INSTALL LH NO.3 TIMING BELT COVER
(a) Install the 3 gaskets to the timing belt cover.
(b) Install the cord grommet to the high±tension cord (from the LH ignition coil).
(c) Install the cord grommet to the timing belt cover.
(d) Fit the portion A of the timing belt cover, matching it with the lower high±tension cord cover.
(e) Install the timing belt cover with the 4 bolts.
32. INSTALL RH ENGINE WIRE COVER
(a) Fit portions A and B of the engine wire cover, matching them with the lower high±tension cord cover and No.3 timing belt
cover.
(b) Install the timing belt cover with the bolt.
33. INSTALL LH ENGINE WIRE COVER
(a) Connect portions A and B of the engine wire cover to the wire
brackets.
(b) Set the VSV (for the fuel pressure) wire in original position.
(c) Fit portions C and D of the engine wire cover, matching them with the lower high±tension cord cover and No.3 timing belt
cover.
(d) Install the timing belt cover with the 2 bolts.
34. INSTALL UPPER HIGH±TENSION CORD COVER
(a) Fit portion A of the upper high±tension cord cover matching the top of the lower high±tension cord cover.
EG±68
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9. REMOVE WATER INLET AND INLET HOUSING
(a) Disconnect the water bypass hose from the IAC valve.
(b) Remove the 2 bolts holding the water inlet housing to waterpump.
(c) Pull out the water inlet and inlet housing assembly.
(d) Remove the O±ring from the water inlet housing.
10. REMOVE TIMING BELT REAR PLATES
Remove the 2 bolts and rear plate. Remove the 2 rear plates.
11. REMOVE VACUUM PIPE
(a) Disconnect the following hoses: (1) California:
Vacuum hose from throttle body
(2) Except California: 3 vacuum hoses from throttle body
(3) Vacuum hose from fuel pressure regulator
(4) 2 vacuum hoses from VSV for fuel pressure control
(5) Except California:
2 vacuum hoses from EGR vacuum modulator
(6) 2 vacuum hoses (from VSV for EVAP) from vacuum pipe
(7) Vacuum hose (from VSV for fuel pressure) from air in-
take chamber
(8) Vacuum hose (from charcoal canister) from vacuum pipe
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(b) Remove the bolt, stud bolt and accelerator bracket.
(c) Remove the union bolt, union and 2 gaskets.
(d) Disconnect the following connectors:wCold start injector connector
w VSV connector for fuel pressure control
w Except California:
VSV connector for EGR
(e) Remove the union bolt and 2 gaskets, and disconnect the cold start injector tube from the RH delivery pipe.
CAUTION:
w Put a shop towel under the delivery pipe.
w Slowly loosen the union bolt.
(f) Remove the 2 bolts and gasket, and disconnect the EGR
pipe from the air intake chamber.
(g) Remove the 4 bolts, 8 nut and following parts: (1) VSV for fuel pressure
(2) Except California:VSV for EGR
(3) Transmission throttle cable bracket
(h) Disconnect the DLC1 from the air intake chamber.
(i) Remove the air intake chamber and 4 gaskets.
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(e) Place 8 new insulators and the 4 spacers in position on theintake manifold.
(f) Place the 8 injectors and 2 delivery pipes assembly in position on the intake manifold.
(g) Temporarily install the connector bracket and 4 nuts.
(h) Check that the injectors rotate smoothly.
HINT: If injectors do not rotate smoothly, the probable cause
is incorrect installation of O±rings. Replace the O±rings.
(i) Position the injector connector upward.
(j) Tighten the 4 nuts holding the delivery pipes to the intake manifold.
Torque: 18 N Vm (185 kgf Vcm, 13 ft Vlbf)
21. INSTALL FUEL RETURN PIPE
(a) Temporarily install the fuel return pipe with the bolt, 2 new
gaskets and union bolt.
(b) Tighten the union bolt holding the return pipe to the fuel pressure regulator.
Torque: 35 N Vm (360 kgf Vcm, 26 ft Vlbf)
(c) Tighten the bolt holding the return pipe to the LH cylinder
head.
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(d) Install a new gasket to the EGR pipe.
(e) Temporarily connect the EGR pipe to the air intake chamberwith the 2 bolts.
HINT: Use bolt 20 mm (0.79 in.) in length.
(f) Temporarily install the air intake and and following parts with the 4 bolts and 8 nuts:
(1) VSV for fuel pressure control
(2) Except California:VSV for EGR
(3) Transmission throttle cable bracket
(4) DLC1
(g) Uniformly tighten the bolts and nuts several passes.
Torque: 18 N Vm (185 kgf Vcm, 13 ft Vlbf)
HINT: Use bolt 40 mm (1.57 in.) in length.
(h) Tighten the 2 bolts holding the EGR pipe to the air intake chamber.
Torque: 18 N Vm (185 kgf Vcm, 13 ft Vlbf)
(i) Tighten the bolt holding the EGR pipe to the RH cylinder
head.
Torque: 18 N Vm (185 kgf Vcm, 13 ft Vlbf)
(j) Connect the cold start injector tube to the RH delivery pipe
with 2 new gaskets and the union bolt.
Torque: 15 N Vm (150 kgf Vcm, 11 ft Vlbf)
(k) Connect the following connectors:
wCold start injector connector
w VSV connector for fuel pressure control
w Except California:
VSV connector for EGR
EG±128
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