1991 LEXUS SC400 exhaust

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Front suspension crossmember x Engine mounting insulator  59 600 43
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PS pump x Cylinder head for bolt 39 400 29
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 for nut 43 440 32
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Propeller shaft x Transmission  79 805 58\
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Propeller shaft x Differential
  
79
 
805
 
58\
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Propeller shaft x Body
  
37
 
375
 
27\
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Center floor crossmember brace x Body  13 130 9\
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Fuel inlet hose x Fuel tube  30 310 22\
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TWC (Front) x Exhaust manifold  62 530 46\
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Front exhaust pipe x TWC (Front)  43 440 32\
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Front exhaust pipe support bracket x Transmission  43 440 32\
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Front exhaust pipe x Center Exhaust pipe  43 440 32\
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Center exhaust pipe x Tailpipe  44 195 14
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Main heated oxygen Exhaust manifold  44 450 33
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Sub heated oxygen sensor x Front exhaust pipe  44 450 33
±
1UZ ± FE ENGINE ENGINE MECHANICALEG±211
WhereEverybodyKnowsYourName

The 1 UZ±FE engine has 8±cylinders in a V±arrangement at a bank an\
gle of 905. From the front of the RH
bank cylinders are numbered 2 ± 4 ± 6 ± 8, and from the front of t\
he LH bank cylinders are 1 ± 3 ± 5 ± 7.
The crankshaft is supported by 5 bearings inside the crankcase. These beari\
ngs are made of a copper and
lead alloy.
The crankshaft is integrated with 8 weights for balance. Oil holes are plac\
ed in the center of the crankshaft
to supply oil to the connecting rods, bearing, pistons and other component\
s.
The ignition order is 1 ± 8 ± 4 ± 3 ± 6 ± 5 ± 7 ± 2. T\
he cylinder head is made of alminum alloy, with a cross
flow type intake and exhaust layout and with pent±roof type combustion chambers. The spark plugs are
located in the center of the combustion chambers.
At the front and rear of the intake manifold, a water passage has been p\
rovided which connects the RH
and LH cylinder heads.
Exhaust and intake valves are equipped with irregular pitch springs made\
of special valve spring carbon
steel which are capable of functioning at all engine speeds.
The RH and LH intake camshaft are driven by a timing belt, and a gear on\
the intake camshaft engages
with a gear on the exhaust camshaft to drive it. The cam journal is supp\
orted at 5 (intake) or 4 (exhaust)
places between the valve lifters of each cylinder and on the front end o\
f the cylinder head. Lubrication of
the cam journals and gears is accomplished by oil being supplied through th\
e oiler port in the center of the
camshaft.
Adjustment of the valve clearance is done by means of an outer shim type\
system, in which valve adjusting
shims are located above the valve lifters. This permits replacement of the sh\
ims without removal of the
camshafts.
Pistons are made of high temperature±resistant aluminum alloy, and a depression is built into the piston
head to prevent interference with the valves.
Piston pins are the full±floating type, with the pins fastened to neither the piston boss nor the connecting
rods. Instead, snap rings are fitted on both ends of the pins, preventing the\
pins from falling out.
The No.1 compression ring is made of steel and the No.2 compression ring\
is made of cast iron. The oil
ring is made of a combination of steel and stainless steel. The outer diamet\
er of each piston ring is slightly
larger than the diameter of the piston and the flexibility of the rings allows them to hug the cylinder walls
when they are mounted on the piston. Compression rings No.1 and No.2 work to\
prevent gas leakage from
the cylinder and the oil ring works to scrape oil off the cylinder walls to prevent it from entering the combus-
tion chambers.
The cylinder block is made of aluminum alloy with a bank of 90 5. Cast iron cylinders are installed inside
the cylinder block. It has 8 cylinders which are approximately twice the le\
ngth of the piston stroke. The top
of each cylinder is closed off by the cylinder head and the lower end of the cylinders becomes the crank-
case, in which the crankshaft is installed. In addition, the cylinder block c\
ontains a water jacket, through
which coolant is pumped to cool the cylinders.
The No.1 and No.2 oil pans are bolted onto the bottom of the cylinder bl\
ock. The No.1 oil pan is made of
aluminum alloy. The No.2 oil pan is an oil reservoir made of pressed steel sheet. An o\
il level sensor is
installed in the No.1 oil pan (If oil level drops below a set level, a warning light\
s up.). And oil pan baffle plate
keeps sufficient oil in the bottom of the No.2 oil pan even when the vehicle is t\
ilted. This dividing plate also
prevents the oil from marking waves when the vehicle is stopped suddenly\
and the oil shifts away from the
oil pump suction pipe.
Plastic region tighten bolts are used for the cylinder head, main bearin\
g cap and connecting rod.
EG±4
±
1UZ±FE ENGINE ENGINE MECHANICAL
WhereEverybodyKnowsYourName

20. INSPECT VALVE CLEARANCE
(a) Check only the valves indicated.wUsing 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):
Intake0.15 ± 0.25 mm (0.006 ± 0.010 in.)
Exhaust 0.25 ± 0.35 mm (0.010 ± 0.014 in.)
(b) Turn the crankshaft 1 revolution (360
) and align the mark as
above. (See procedure in step 8)
(c) Check only the valves indicated as shown. Measure the valve
clearance. (See procedure in step (a))
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.
EG±20
±
1UZ±FE ENGINE ENGINE MECHANICAL
WhereEverybodyKnowsYourName

wUsing compressed air and a magnetic finger, remove
the adjusting shim by blowing air into the shim hole.
HINT: Remove the adjusting shim from the intake manifold
side.
NOTICE: Do not drop the adjusting shim into portions A and
B. If dropped into portion A, the adjusting shim will pass
through the cylinder head and cylinder block into the oil pan.
If dropped into portion B, the adjusting shim cannot be recov-
ered without removing the exhaust camshaft.
EG±22±
1UZ±FE ENGINE ENGINE MECHANICAL
WhereEverybodyKnowsYourName

(b) Determine the replacement adjusting shim size by followingthe Formula or Charts:
wUsing a micrometer, measure the thickness of the
removed shim.
w Calculate the thickness of a new shim so that the valve
clearance comes within specified value.
T 000 Thickness of removed shim
A 000 Measured valve clearance
N 000 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 value.
HINT: Shims are available in 33 sized 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. wPlace a new adjusting shim on the valve lifter.
w Using SST (A), press down the valve lifter and remove
SST (B).
SST 09248±05410, 09248±05021
(d) Recheck the valve clearance.
±
1UZ±FE ENGINE ENGINE MECHANICALEG±23
WhereEverybodyKnowsYourName

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\
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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\
 

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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±
1UZ±FE ENGINE ENGINE MECHANICAL
WhereEverybodyKnowsYourName

(b) Remove the nut and 3 bolts, and disconnect the PS pumpfrom the engine.
5. REMOVE TWC (FRONT)
(a) Remove the 4 bolts holding the pipe support bracket to the transmission.
(b) Remove the 4 bolts and nuts holding the front exhaust pipe to the TWC, and remove the pipe support bracket.
(c) Disconnect the front exhaust pipe from the TWC, and remove
the 2 gaskets.
(d) Using a 14 mm deep socket wrench, remove the 3 nuts, TWC
and gasket. Remove the 2 TWC.
6. REMOVE THROTTLE BODY COVER
(a) Disconnect the EVAP hose from the hose clamp.
(b) Remove the cap nut.
(c) Loosen the 2 bolts, and remove the hose clamp and throttle body cover.
7. DISCONNECT CONTROL CABLES FROM THROTTLE BODY
Disconnect the following cables:
(1) Accelerator cable
(2) Transmission throttle control cable
(3) Cruise control actuator cable
8. REMOVE RH IGNITION COIL
(a) Disconnect the ignition coil connector.
(b) Remove the 2 bolts and ignition coil.
EG±76
±
1UZ±FE ENGINE ENGINE MECHANICAL
WhereEverybodyKnowsYourName

30. REMOVE OIL DIPSTICK AND GUIDE FORTRANSMISSION
(a) Remove the bolt holding the oil dipstick to the LH cylinder head.
(b) Pull out the dipstick guide together with the dipstick from the oil pan.
(c) Remove the O±ring from the dipstick guide.
31. REMOVE OIL DIPSTICK AND GUIDE FOR ENGINE
32. REMOVE EGR PIPE
(a) Remove the 2 bolts holding the EGR pipe to the RH exhaust pipe.
(b) Remove the EGR pipe and gasket.
33. DISCONNECT ENGINE WIRE FROM CYLINDER HEADS
(a) Remove the 2 bolts, and disconnect the engine wire protector
from the RH cylinder head.
(b) Remove the bolt, and disconnect the ground strap from the RH cylinder head.
(c) Remove the 5 bolts, and disconnect the engine wire protector
from the LH cylinder head.
34. REMOVE ENGINE HANGERS Remove the 2 bolts and engine hanger. Remove the 2 engine
hangers.
±
1UZ±FE ENGINE ENGINE MECHANICALEG±85
WhereEverybodyKnowsYourName