Lexus SC300 / Lexus SC400. Manual — part 354

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 “LOCK” 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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1UZ–FE ENGINE

ENGINE MECHANICAL

EG–37

5.

REMOVE RH ENGINE WIRE COVER
Remove the bolt and engine wire cover.

6.

REMOVE LH ENGINE WIRE COVER
Remove the 2 bolts and engine wire cover.

7.

REMOVE VSV FOR EVAP SYSTEM
Remove the 2 bolts, and disconnect the VSV from the cylin-
der head cover and timing belt cover.

8.

REMOVE RH NO.3 TIMING BELT COVER
Remove the 3 bolts, timing belt cover and 3 gaskets.

9.

REMOVE LH NO.3 TIMING BELT COVER

(a) Remove the 4 bolts
(b) Disconnect the cord grommet from the timing belt cover, and

remove the timing belt cover and 3 gaskets.

(c) Remove the cord grommet from the high–tension cord.

EG–38

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1UZ–FE ENGINE

ENGINE MECHANICAL

10. DISCONNECT COLD START INJECTOR CONNECTOR

11. DISCONNECT RH CAMSHAFT POSITION SENSOR

CONNECTOR

(a) Disconnect the connector from the ignition coil bracket.
(b) Disconnect the camshaft position sensor connector.

12. DISCONNECT LH CAMSHAFT POSITION SENSOR

CONNECTOR

13. DISCONNECT HIGH–TENSION CORDS FROM SPARK

PLUGS
Disconnect the high–tension cords at the rubber boot. Do not
pull on the cords.

NOTICE: Pulling on or bending the cords may damage the con-

ductor inside.

14. REMOVE SPARK

PLUGS

Using a 16 mm plug wrench, remove the 8 spark plugs.

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1UZ–FE ENGINE

ENGINE MECHANICAL

EG–39

15. CHECK CYLINDER COMPRESSION PRESSURE
(a) Reconnect the battery negative (–) cable.
(b) Insert a compression gauge into the spark plug hole.
(c) Fully open the throttle.
(d) While cranking the engine, measure the compression

pressure.
HINT: Always use a fully charged battery to obtain engine
speed of 250 rpm or more.

(e) Repeat steps (b) through (d) for each cylinder.

NOTICE: This measurement must be done in as short a
time as possible.

Compression pressure:

1,226 kPa (12.5 kgf/cm

2

, 178 psi) or more

Minimum pressure:

981 kPa (10.0 kgf/cm

2,

142 psi)

Difference between each cylinder:

98 kPa (1.0 kgf/cm

2

, 14 psi) or less

(f) If the cylinder compression in one or more cylinders is low,

pour a small amount of engine oil into the cylinder through the
spark plug hole and repeat steps (b) through (d) for cylinders
with low compression.

•

If adding oil helps the compression, it is likely that the
piston rings and/or cylinder bore are worn or damage.

•

If pressure stays low, a valve may be sticking or seating
is improper, or there may be leakage past the gasket.

(g) Disconnect the battery negative (–) cable.

16. REINSTALL

SPARK

PLUGS

Using a 16 mm plug wrench, install the 8 spark plugs.

Torque: 18 N

⋅

m (180 kgf

⋅

cm, 13 ft

⋅

lbf)

17. RECONNECT HIGH–TENSION CORDS TO SPARK

PLUGS

18. RECONNECT RH CAMSHAFT POSITION SENSOR

CONNECTOR

(a) Connect the camshaft position sensor connector.
(b) Install the camshaft position sensor connector to the ignition

coil bracket.

EG–40

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1UZ–FE ENGINE

ENGINE MECHANICAL