LEXUS SC400 1991 Service Repair Manual

INSPECTION AND ADJUSTMENT OF
VALVE CLEARANCE
HINT: Inspect and adjust the valve clearance when the
engine is cold.
1. DISCONNECT CABLE FROM NEGATIVE TERMINAL OF BATTERY
CAUTION: Work must be started after approx. 20 se-
conds or longer from the time the ignition switch is
turned to the ºLOCKº position and the negative (±) termi-
nal cable is disconnected from the battery.
2. DRAIN ENGINE COOLANT (See page CO±6)
3. REMOVE THROTTLE BODY COVER (a) Remove the mounting cap nut.
(b) Loosen the two bolts, and remove the throttle body
cover.
4. DISCONNECT CONTROL CABLES FROM THROTTLE BODY
Disconnect the following cables:(1) Accelerator cable
(2) A/T throttle control cable
(3) (w/ Cruise Control System) Cruise control actuator cable
5. REMOVE INTAKE AIR CONNECTOR (a) Disconnect the following hoses:(1) Air hose from ISC valve
(2) Air hose (from PS air control valve) from intake
air connector
(b) Remove the bolt holding the intake air connector to the cylinder head cover.
(c) Loosen the two hose clamps.
(d) Disconnect the intake air connector from the throttle
body and air cleaner hose, and remove the throttle body.
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6. REMOVE UPPER HIGH±TENSION CORD COVER(a) Remove the two mounting bolts.
(b) Disconnect the front side claw groove of the cord coverfrom the claw of the lower cover, and remove the cord
cover.
7. REMOVE RH ENGINE WIRE COVER Remove the bolt and engine wire cover.
8. REMOVE LH ENGINE WIRE COVER Remove the two bolts and engine wire cover.
9. REMOVE VSV FOR EVAP SYSTEM Remove the two bolts, and disconnect the VSV from cylinder
head and timing belt cover.
10. REMOVE RH NO.3 TIMING BELT COVER Remove the three bolts and timing belt cover.
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11. DISCONNECT FUEL INLET HOSE FROM LH DELIVERYPIPE
Remove the pulsation damper and two gaskets, and discon-
nect the inlet hose.
12. D I S C O N N E C T F U E L R E T U R N H O S E F R O M F U E L RETURN PIPE
13. DISCONNECT PCV HOSE FROM LH CYLINDER HEAD
14. REMOVE LH NO.3 TIMING BELT COVER (a) Remove the four mounting bolts.
(b) Disconnect the cord grommet from the timing belt cover,
and remove the timing belt cover.
(c) Remove the cord grommet from the high±tension cord.
15. DISCONNECT HEATER WATER VALVE FROM BODY (a) Disconnect the VSV connector.
(b) Remove the bolt holding the engine wire clamp to thewater valve bracket.
(c) Remove the two bolts, and disconnect the water valve and bracket assembly.
16. REMOVE THROTTLE BODY (a) Disconnect the following connectors:(1) Throttle position sensor connector
(2) (w/ TRAC)
Sub±throttle position sensor connector
(3) (w/ TRAC) Sub±throttle actuator connector
(b) Disconnect the following hoses: (1) Water by±pass hose from ISC valve
(2) (USA Spec.) Vacuum hose from throttle body
(3) (Exc. USA Spec.) Three vacuum hoses from throttle body
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(c) Remove the two bolts and two nuts, disconnect thethrottle body from the air intake chamber.
(d) Disconnect the following hoses, and remove the throttle body:
(1) PCV hose from throttle body
(2) Water by±pass hose from throttle body
(e) Remove the throttle body gasket.
17. REMOVE RH CYLINDER HEAD COVER (a) Remove the two bolts holding the cord clamp to thecylinder head.
(b) Disc onnect the high±tension cords from the spark
plugs.
(c) Disconnect the high±tension cords from the front high±tension cord clamp.
(d) Remove the eight bolts, seal washers, cylinder head cover and gasket.
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16. REMOVE LH CYLINDER HEAD COVER(a) Remove the two bolts holding the high±tension cordclamp to the cylinder head.
(b) Disc onnect the high±tension cords from the spark
plugs.
(c) Disconnect the high±tension cords from the front high±tension cord clamp.
(d) Disconnect the engine wire from the two wire clamps on
the LH delivery pipe.
(e) Disconnect the four injector connectors.
(f) Disconnect the two engine wire connectors.
(g) Remove the eight bolts, seal washers, cylinder head
cover and gasket.
19. SET NO.1 CYLINDER TO TDC/COMPRESSION (a) Turn the crankshaft pulley, and align its groove with thetiming mark º0º of the No.1 timing belt cover.
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(b) Check that the timing marks of the camshaft timingpulleys and timing belt rear plates aligned.
If not, turn the crankshaft one revolution (360 5) and align the
mark as above.
20. INSPECT VALVE CLEARANCE (a) Check only those valves indicated.w Using a feeler gauge, measure the clearance
between the valve lifter and camshaft.
w Record the out±of±specification valve clearance
measurements. They will be used later to
determine the required replacement adjusting
shim.
Valve clearance (Cold):
Intake 0.15±0.25 mm (0.006±0.010 in.)
Exhaust 0.25±0.35 mm (0.010±0.014 in.)
(b) Turn the crankshaft one revolution (360 °), and align the
mark as above. (See procedure step in 19 (a))
(c) Check only the valves indicated as shown. Measure the
valve clearance.
(See procedure in step (a))
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21. REMOVE THEFT DETERRENT HORN(a) Disconnect the connector.
(b) Remove the bolt and theft deterrent horn.
HINT: Remove the deterrent horn when the valve clearance
is adjusted for the front portion of the exhaust camshaft on
the LH cylinder head.
22. ADJUST VALVE CLEARANCE (a) Remove the adjusting shim.w Turn the crankshaft, and position the cam lobe of
the camshaft on the adjusting valve upward.
w Position the hole of the adjusting shim toward the
spark plug side.
w Press down the valve lifter with SST (A), and place
SST (B) between the camshaft and valve lifter
flange. Remove SST (A).
SST 09248±55011 (09248±05011 (A), 09248±05021 (B))
NOTICE: The valve lifter is made of aluminum, which is
easily scratched. So when setting SST (B), take care not
to scratch the face of the valve lifter.
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Using compressed air and magnetic finger, removethe adjusting shim by blowing air into the shim hole.
HINT: Remove the adjusting shim from the intake man-
ifold side.
NOTICE: Do not drop the adjusting shim into por-
tions A and B. If dropped into portion A, the adjust-
ing shim will pass through the cylinder head and
cylinder block into the oil pan. If dropped into por-
tion B, the adjusting shim cannot be recovered with-
out removing the exhaust camshaft.
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(b) Determine the replacement adjusting shim sizefollowing Formula or Charts:
w Using a micrometer, measure the thickness of the
removed shim.
w Calculate the thickness of a new shim so the valve
clearance comes within specified value.
T
Thickness of used shim
A
Measured valve clearance
N
Thickness of new shim
Intake N = T + (A±0.20 mm (0.008 in.))
Exhaust N = T + (A±0.30 mm (0.012 in.))
w Select a new shim with a thickness as close as
possible to the calculated values.
HINT: Shims are available in thirty±three sizes in increments
of 0.025 mm (0.0010 in.), from 2.50 mm (0.0984 in.) to 3.30
mm (0.1299 in.).
(c) Install a new adjusting shim. w Place a new adjusting shim on the valve lifter.
w Press down the valve lifter with SST (A), and
remove SST (B).
SST 09248±55011
(d) Recheck the valve clearance.
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Adjusting Shim Selection Chart (Intake)
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