1991 LEXUS SC400 check engine

IDLE AND/OR 2,500 RPM CO/HC
CHECK
EG116±05
HINT: This check is used only to determine whether or not the
idle CO/HC complies with regulations.
1. INITIAL CONDITIONS
(a) Engine at normal operating temperature
(b) Air cleaner installed
(c) All pipes and hoses of air induction system connected
(d) All accessories switched OFF
(e) All vacuum lines properly connected
HINT: All vacuum hoses for EGR system, etc. should be prop-
erly connected.
(f) MFI system wiring connectors fully plugged
(g) Ignition timing set correctly
(h) Transmission in neutral position
(i) Tachometer and CO/HC meter calibrated by hand
2. START ENGINE
3. RACE ENGINE AT 2,500 RPM FOR APPROX. 180 SECONDS
4. INSERT CO/HC METER TESTING PROBE INTO TAILPIPE AT LEAST 40 cm (1.3 ft) DURING IDLING
5. IMMEDIATTELY CHECK CO/HC CONCENTRATION AT
IDLE AND/OR 2,500 RPM
HINT: When performing the 2 mode (2,500 rpm and idle) test,
follow the measurement order prescribed by the applicable
local regulations.
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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\
 \
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\
 

\
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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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) Wh ile cra n kin g th e en g in e , me a su re th e co mp re ssio npressure.
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 sm all amount of engine oil into the cylinder through the
spark plug hole and repeat steps (b) through (d) for cylinders
with low compression.
w If adding oil helps the compression, it is likely that the
piston rings and/or cylinder bore are worn or damage.
w 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 Vm (180 kgf Vcm, 13 ft Vlbf)
17. R E C O N N E C T H I G H ± T E N S I O N C O R D S TO S PA R K
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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25. REMOVE SPARK PLUGSUsing a 16 mm plug wrench, remove the 8 spark plugs.
26. IF RE±USING TIMING BELT, CHECK INSTALLATION MARKS ON TIMING BELT
Check that there are 4 installation marks on the timing belt by
turning the crankshaft pulley as shown in the illustration.
HINT: If the installation marks have disappeared, place a new
installation mark on the timing belt before removing each
part.
27. SET NO.1 CYLINDER TO TDC/COMPRESSION
(a) Turn the crankshaft pulley and align its groove with timing mark ª0º of the No.1 timing belt cover.
(b) Check that the timing marks of the camshaft timing pulleys and timing belt rear plates aligned.
If not, turn the crankshaft 1 revolution (360 5).
28. REMOVE TIMING BELT TENSIONER HINT:
wWhen re±using timing belt:
If the installation marks have disappeared, before re-
move the timing belt, place new installation marks on
the timing belt to match the timing marks of the camshaft
timing pulleys, and place the a new installation mark on
the timing belt to match the end of the hydraulic pump.
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39. REMOVE CRANKSHAFT TIMING PULLEYUsing SST, remove the timing pulley.
SST 09213±60017 (09213±00050)
EG1KH±02
TIMING BELT COMPONENTS
INSPECTION
1. INSPECT TIMING BELT
NOTICE:
w Do not bend, twist or turn the timing belt inside out.
w Do not allow the timing belt to come into contact with oil,
water or steam.
w Do not utilize timing belt tension when installing or
removing the mounting bolt of the camshaft timing
pulley.
If there are any defects as shown in the illustration, check the
following points:
(a) Premature parting wCheck the proper installation.
w Check the timing cover gasket for damage and proper
installation.
(b) If the belt teeth are cracked or damaged, check to see if either
camshaft or water pump is locked.
(c) If there is noticeable wear or cracks on the belt face, check to see if there are nicks on the side of the idler pulley lock.
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(d) If there is wear or damage on only one side of the belt, checkthe belt guide and the alignment of each pulley.
(e) If there is noticeable wear on the belt teeth, check the timing cover for damage, gasket has been installed correctly, and
the foreign material on the pulley teeth. If necessary, replace
the timing belt.
2. INSPECT IDLER PULLEYS Check that the idler pulley turns smoothly.
If necessary, replace the idler pulley.
3. INSPECT TIMING BELT TENSIONER
(a) Visually check tensioner for leakage. HINT: If there is only the faintest trace of oil on the seal on the
push rod side, the tensioner is all right.
If leakage is found, replace the tensioner.
(b) Hold the tensioner with both hands, and push the push rod firmly against floor or wall to check that it doesn't move.
If push rod moves, replace the tensioner.
EG±58
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(c) Measure the protrusion of the push rod from the housing end.
Protrusion:
10.5 ± 11.5 mm (0.413 ± 0.453 in.)
If the protrusion is not as specified, replace the tensioner.
EG21R±02
TIMING BELT INSTALLATION
See Components for Removal and Installation:
1. INSTALL CRANKSHAFT TIMING PULLEY
(a) Align the timing pulley set key with the key groove of thepulley.
(b) Using SST and a hammer, tap in the timing pulley, facing the flange side inward.
SST 09223±46011
2. INSTALL NO.1 IDLER PULLEY
(a) Apply adhesive 2 or 3 threads of the pivot bolt.
Adhesive: Part No. 08833±00080, THREE BOND 1344,
LOCTITE 242 or equivalent
(b) Using a 10 mm hexagon wrench, install the plate washer and
idler pulley with the pivot bolt.
Torque: 34 N Vm (350 kgf Vcm, 25 ft Vlbf)
(c) Check that the pulley bracket moves smoothly.
3. INSTALL NO.2 IDLER PULLEY
(a) Install the idler pulley with the bolt.
Torque: 34 N Vm (350 kgf Vcm, 25 ft Vlbf)
(b) Check that the idler pulley moves smoothly.
4. TEMPORARILY INSTALL TIMING BELT
NOTICE: The engine should be cold.
(a) Using the crankshaft pulley bolt, turn the crankshaft and align
the timing marks of the crankshaft timing pulley and oil pump
body.
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