1991 LEXUS SC400 spark plugs

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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ENGINE MECHANICAL Engine Tune±UpEM±15
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23. REINSTALL THEFT DETERRENT HORN(a) Install the theft deterrent horn with the bolt.
(b) Connect the connector.
24. REINSTALL RH CYLINDER HEAD COVER (a) Remove any oil packing (FIPG) material.
(b) Apply seal packing to the cylinder head as shown in theillustration.
Seal packing: Part No. 08826±00080 or equivalent
(c) Install the gasket to the cylinder head cover.
(d) Install the seal washer to the mounting bolt.
(e) Install the cylinder head cover with the eight bolts.
Torque: 5.9 N Vm (60 kgf Vcm, 52 in. Vlbf)
(g) Connect the four high±tension cords to the spark plugs.
(h) Install the rear and front high±tension cord clamps with
the two bolts.
HINT: Place the front and rear ends of the front high±tension
cord clamp on the rear high±tension cord clamp and lower
high±tension cord cover.
(i) Fit the high±tension cords to the high±tension cord clamps. (See page IG±16)
25. REINSTALL LH CYLINDER HEAD COVER (a) Remove any oil packing (FIPG) material.
(b) Apply seal packing to the cylinder head as shown in theillustration.
Seal packing: Part No. 08826±00080 or equivalent
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(c) Install the gasket to the cylinder head cover.
(d) Install the seal washer to the mounting bolt.
(e) Install the cylinder head cover with the eight bolts.
Torque: 5.9 NVm (60 kgf Vcm, 52 in. Vlbf)
(f) Connect the two engine wire connectors.
(g) Connect the four injector connectors.
(h) Install the engine wire to the two wire clamps on the
delivery pipe.
(i) Connect the four high±tension cords to the spark plugs.
(j) Install the rear and front high±tension cord clamps with the two bolts.
HINT: Place the front and rear ends of the front high±tension
cord clamp on the rear high±tension cord clamp and lower
high±tension cord cover.
(k) Fit the high±tension cords to the high±tension cord clamps. (See page IG±16)
26. REINSTALL THROTTLE BODY (a) Connect the following hoses:(1) PCV hose from throttle body
(2) Water by±pass hose from throttle body
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ENGINE MECHANICAL Engine Tune±UpEM±23
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COMPRESSION CHECK
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. REMOVE NO.3 TIMING BELT COVERS (See steps 1, 5 to 10 and 14 on pages EM±11 to 13)
3. DISCONNECT COLD START INJECTOR CONNECTOR
4. DISCONNECT RH CAM POSITION SENSOR CONNECTOR
(a) Disconnect the connector from the ignition coil bracket.
(b) Disconnect the sensor connector.
5. DISCONNECT LH CAM POSITION SENSOR CONNECTOR
6. REMOVE SPARK PLUGS (a) Disconnect the eight high±tension cords from the sparkplugs.
Disconnect the high±tension cords at rubber boot. Do
not pull on the cords.
NOTICE: Pulling on or bending the cords may damage
the conductor inside.
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ENGINE MECHANICAL Compression Check
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(b) Using a 16 mm spark plug wrench, remove the eightspark plugs.
7. CHECK CYLINDER COMPRESSION PRESSURE (a) Insert a compression tester into the spark plug hole.
(b) Fully open the throttle.
(c) While cranking the engine, measure the compressionpressure.
HINT: Always use a fully charged battery to obtain engine rev-
olution of 250 rpm or more.
(d) Repeat steps (a) through (c) for each cylinder.
NOTICE: This measurement must be done in as short
time as possible.
Compression pressure:
1,226 kPa (12.5 kgf/cm, 178 psi) or more
Minimum pressure: 981 kPa (10.0 kgf/cm, 142 psi)
Difference between each cylinder:
98 kPa (1.0 kgf/cm, 14 psi) or less
(e) If the cylinder compression in one or more cylinders islow, pour a small amount of engine oil into the cylinder
through the spark plug hole and repeat steps (a) through
(c) for the cylinder with low compression.
w If adding oil helps the compression the piston rings
and/or cylinder bore are probably worn or
damaged.
w If pressure stays low, a valve may be sticking or
seating improper, or there may be leakage past the
gasket.
8. REINSTALL SPARK PLUGS (a) Using a 16 mm plug wrench, install the eight sparkplugs.
Torque: 18 N Vm (180 kgf Vcm, 13 ft Vlbf)
(b) C onnect the eight high±tension cords to the spark
plugs.
(c) Fit the high±tension cords to the cord clamps.
(See page IG±16)
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15. REMOVE HIGH±TENSION CORDS, HIGH±TENSIONCORD CLAMPS AND LOWER HIGH±TENSION CORD
COVER ASSEMBLY
(a) Remove the two bolts holding the RH rear high±tensioncord clamp to the cylinder head.
(b) Disconnect the high±tension cords from the RH spark plugs and distributor cap.
(c) Remove the two bolts holding the LH rear high±tension cord clamp to the cylinder head.
(d) Disconnect the high±tension cords from the LH spark
plugs, distributor cap and LH ignition coil.
(e) Remove the bolt holding the lower high±tension cord cover to the water inlet housing.
(f) Disconnect the high±tension cord from the RH ignition
coil, and remove the high±tension cords, clamps and
cover assembly.
16. REMOVE DRIVE BELT IDLER PULLEY Remove the pulley bolt, cover plate and idler pulley.
17. REMOVE RH NO.2 TIMING BELT COVER (a) Disconnect the cam position sensor connector from theignition coil bracket.
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ENGINE MECHANICAL Timing Belt
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22. REMOVE ALTERNATOR(a) Disconnect the alternator connector.
(b) Remove the cap and nut, and disconnect the alternatorwire.
(c) Remove the bolt, and disconnect the A/T oil cooler pipe bracket.
(d) Remove the nut and alternator.
23. REMOVE DRIVE BELT TENSIONER Remove the bolt, two nuts and tensioner.
24. REMOVE SPARK PLUGS Using a 16 mm plug wrench, remove the eight spark plugs.
25. IF RE±USING TIMING BELT, CHECK INSTALLATION MARKS ON TIMING BELT
Check that there are four installation marks on the timing belt
by turning the crankshaft pulley as shown in the illustration.
If the installation marks have disappeared, place a new
installation mark on the timing belt before removing each
part.
26. SET NO.1 CYLINDER TO TDC/COMPRESSION (a) Turn the crankshaft pulley and align its groove with thetiming mark ºOº of the No.1 timing belt cover.
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ENGINE MECHANICAL Timing Belt
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16. INSTALL TIMING BELT TENSIONER(a) Temporarily install the tensioner with the two bolts.
(b) Alternately tighten the two bolts.
Torque: 26 N Vm (270 kgf Vcm, 20 ft Vlbf)
(c) Using pliers, remove the 1.27 mm hexagon wrench from
the tensioner.
17. CHECK VALVE TIMING (a) Turn the crankshaft pulley two revolutions from TDC toTDC.
NOTICE: Always turn the crankshaft clockwise.
(b) Check that each pulley aligns with the timing marks as shown in the figure.
If the marks do not align, remove the timing belt and reinstall
it.
18. INSTALL SPARK PLUGS Using a 16 mm plug wrench, install the eight spark plugs.
Torque: 18 N Vm (180 kgf Vcm, 13 ft Vlbf)
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ENGINE MECHANICAL Timing BeltEM±51
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