1991 LEXUS SC400 check engine

PRECAUTIONS
1. Do not leave the ignition switch on for more than 10minutes if the engine will not start.
2. With a tachometer connected to the system, connect the tester probe of the tachometer to terminal IG
of the
check (ºDIAGNOSISº) connector.
HINT:
wAllow the engine to warm up to normal operation
temperature.
w Set the tachometer to the 4±cylinder range.
3. As some tachometers are not compatible with this ignition system, we recommend that you confirm the
compatibility of your unit before use.
4. Never allow the tachometer terminal to touch ground as this could damage the igniter and/or ignition coil.
5. Do not disconnect the battery when the engine is running.
6. Check that the igniter is properly grounded to the body.
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IGNITION SYSTEM PrecautionsIG±3
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ON±VEHICLE INSPECTION
SPARK TEST
CHECK THAT SPARK OCCURS(a) Remove the No.3 timing belt covers.(See steps 2 to 8 on pages IG±11 to 13)
(b) Disconnect the high±tension cords (from the ignition
coils) from the distributor caps.
(c) Hold the end about 12.5 mm (0.50 in.) from the body ground.
(d) Check if spark occurs while engine is being cranked.
HINT: To prevent gasoline from being injected from injectors
during this test, crank the engine for no more than 1±2 se-
conds at a time.
If the spark does not occur, perform the test as follows:
(e) Reconnect the high±tension cords to the distributor caps.
(f) Reinstall the No.3 timing belt covers. (See steps 5 to 11 on pages IG±17 to 19)
IG±6
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IGNITION SYSTEM On±Vehicle Inspection
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INSPECTION OF HIGH±TENSION CORDS
1. REMOVE HIGH±TENSION CORDS(See steps 1 to 9 on pages IG±11 to 14)
2. INSPECT HIGH±TENSION CORD RESISTANCE
Using an ohmmeter, measure the resistance.
Maximum resistance: 25 k
per cord
If the resistance is greater than maximum, replace the high±
tension cord.
3. REINSTALL HIGH±TENSION CORDS (See steps 4 to 13 on pages IG±11 to 19)
INSPECTION OF SPARK PLUGS
NOTICE:
wNever use a wire brush for cleaning.
w Never attempt to adjust the electrode gap on used spark
plug.
w Spark plug should be replaced every 100,000 km (60,000
miles).
1. DISCONNECT HIGH±TENSION CORDS FROM SPARK
PLUGS (See steps 1 to 9 on pages IG±11 to 13)
2. INSPECT ELECTRODE
Using a megger (insulation resistance meter), measure the
insulation resistance.
Correct insulation resistance: 10 M
or more
If the resistance is less than specified, proceed to step 4.
HINT: If a megger is not available, the following simple meth-
od of inspection provides fairy accurate results.
(Simple Method)
(a) Quickly race the engine to 4,000 rpm five times.
(b) Remove the spark plug. (See step 3)
(c) Visually check the spark plug.
If the electrode is dry. . . . . Okay
If the electrode is wet . . . . . Proceed to step 4
(d) Reinstall the spark plug.
(See step 7 on page IG±8)
3. REMOVE SPARK PLUGS Using a 16 mm plug wrench, remove the spark plugs.
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IGNITION SYSTEM On±Vehicle InspectionIG±7
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(b) Push the front side of the high±tension cord cover, andconnect 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 two bolts.
11. INSTALL INTAKE AIR CONNECTOR (a) Connect the end portions of the intake air connector tothe throttle body and air cleaner hose.
(b) Tighten the two hose clamps.
(c) Install the bolt holding the intake air connector to the cylinder head cover.
(d) Connect the following hoses: (1) Air hose to ISC valve
(2) Air hose (from PS air control valve) to intake air con-
nector
12. CONNECT CABLE TO NEGATIVE TERMINAL OF BATTERY
13. CHECK THAT ENGINE STARTS
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IGNITION SYSTEM High±Tension Cords and Cord ClampsIG±19
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9. INSTALL DRIVE BELT IDLER PULLEYInstall the idler pulley and cover plate with the pulley bolt.
Torque: 37 N Vm (380 kgf Vcm, 27 ft Vlbf)
10. INSTALL NO.3 TIMING BELT COVERS
(See steps 5 to 9 and 11 on pages IG±17 to 19)
11. CONNECT RADIATOR HOSE TO WATER INLET
12. C O N N E C T C A B L E TO N E G AT I V E T E R M I N A L O F BATTERY
13. FILL ENGINE WITH COOLANT (See page CO±6)
14. WARM UP ENGINE Allow the engine to warm up to normal operating tempera-
ture.
15. CONNECT TACHOMETER Connect the tester probe of a tachometer to terminal IG
of
the check (ºDIAGNOSISº) connector.
HINT: Set the tachometer to the 4±cylinder range.
NOTICE:
w Never allow the tachometer tester probe to touch ground
as it could result in damage to the igniter and/or ignition
coil.
w As some tachometers are not compatible with this
ignition system, we recommend that you confirm the
compatibility of your unit before use.
16. CHECK IGNITION TIMING
(a) Using SST, connect terminals TE1 and E1 of the check(ºDIAGNOSISº) connector.
SST 09843±18020
(b) C onnect the tester probe of a timing light to the
high±tension cord for No.6 cylinder.
IG±28
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IGNITION SYSTEM Distributor
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(c) Check the ignition timing.
Ignition timing: 8±125 BTDC @ idle
(Transmission in neutral range)
If the ignition timing is not as specified, check that following
conditions are normal: w Throttle valve fully closed
w Continuity between terminals IDL1 and E2 of the
throttle position sensor (See page FI±73)
w Valve timing (See page EM±51)
(e) Remove the SST from the check connector.
SST 09843±18020
17. DISCONNECT TACHOMETER AND TIMING LIGHT FROM ENGINE
18. INSTALL UPPER HIGH±TENSION CORD COVER (See step 10 on pages IG±18 and 19)
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IGNITION SYSTEM DistributorIG±29
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A pressure feeding lubrication system has been adopted to supply oil to \
the moving parts of this engine. The
lubrication system consists of an oil pan, oil pump, oil filter and other external p\
arts which supply oil to the moving
parts in the engine block. The oil circuit is shown in the illustration at th\
e top of the previous page. Oil from the
oil pan is pumped up by the oil pump. After it passes through the oil fi\
lter, it is fed through the various oil holes
in the crankshaft and cylinder block. After passing through the cylinder b\
lock and performing its lubricating func-
tion, the oil is returned by gravity to the oil pan. A dipstick on the center\
left side of the cylinder block is provided
to check the oil level.
OIL PUMP The oil pump pumps up oil from the oil pan and sends it under pressure to t\
he various parts of the engine.
An oil strainer is mounted in front of the inlet to the oil pump. The oil \
pump itself is a trochoid type pump, inside
of which there is a drive rotor and a driven rotor. When the drive rotor rotates, the driven rotor rotates in the same
direction, and since the axis of the driven rotor shaft is different from the center of the driven rotor, the space
between the two rotors is changed as they rotate. Oil is drawn in when the space\
is wide and is discharged when
the space in narrow.
OIL PRESSURE REGULATOR At high engine speeds, the engine oil supplied by the oil pump exceeds the\
capacity of the engine to utilize
it. For that reason, the oil pressure regulator works to prevent an over\
supply of oil. During normal oil supply, a
coil spring and valve keep the bypass closed, but when too much oil is being \
fed, the pressure become extremely
high, overpowering the force of the spring and opening the valves. This allow\
s the excess oil to flow through
the valve and return to the oil pump inlet.
OIL FILTER The oil filter is a full flow type filter with a built±in paper filter e\
lement. Particles of metal from wear, airborne
dirt, carbon and other impurities can get into the oil during use and co\
uld cause accelerated wear or seizing if
allowed to circulate through the engine. The oil filter, integrated into the oil line, removes these impurities as the
oil passes through it. The filter is mounted outside the engine to simplify\
replacement of the filter element. A relief
valve is also included ahead of the filter element to relieve the high oil pr\
essure in case the filter element be-
comes clogged with impurities. The relief valve opens when the oil pressure o\
verpowers the force of the spring.
Oil passing through the relief valve by±passes the oil filter and flo\
ws directly into the main oil hole in the engine.
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LUBRICATION SYSTEM PrecautionsLU±3
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OIL PRESSURE CHECK
1. CHECK ENGINE OIL QUALITYCheck the oil for deterioration, presence of water, discoloring
or thinning.
If the quality is poor, replace the oil.
Oil grade: API grade SG, Energy±Conserving II multigrade.
Recommended viscosity is as shown, with SAE 5W±30 being
the preferred engine oil.
2. CHECK ENGINE OIL LEVELThe oil level should be between the ºLº and ºFº marks on the
dipstick.
If low, check for the leakage and add oil up to ºFº mark.
3. REMOVE ENGINE UNDER COVER
4. REMOVE DRIVE BELT Loosen the drive belt tension by turning the drive belt tension-
er clockwise, and remove the drive belt.
5. DISCONNECT A/C COMPRESSOR WITHOUT DISCONNECTING HOSES
(a) Disconnect the compressor connector.
(b) Remove the four mounting bolts and nut.
(c) R e m o v e t h e t h r ought bolt, and disconnect the
compressor from the engine.
HINT: Put aside the compressor, and suspend it.
6. REMOVE OIL PRESSURE SWITCH, AND INSTALL OIL PRESSURE GAUGE
(a) Disconnect the oil pressure switch connector.
(b) Using SST, remove the oil pressure switch.SST 09816±30010
(c) Install an oil pressure gauge.
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LUBRICATION SYSTEM Oil pressure CheckLU±5
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