Nissan Xterra. Instruction — part 348

EM-20

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[VQ40DE]

CAMSHAFT VALVE CLEARANCE

d. Rotate crankshaft by 240

° clockwise (when viewed from engine

front) to align No. 5 cylinder at TDC of compression stroke.

• Measure the valve clearances at locations marked “

×” as

shown in the table below (locations indicated in the illustration)

with feeler gauge.

• No. 5 cylinder at compression TDC

4. For the measured value out of the standard, perform adjustment.

ADJUSTMENT

• Perform adjustment depending on selected head thickness of valve lifter.
1. Measure the valve clearance.
2. Remove camshaft. Refer to

EM-76, "Removal and Installation"

.

3. Remove valve lifters at the locations that are out of the standard.
4. Measure the center thickness of removed valve lifters with

micrometer.

5. Use the equation below to calculate valve lifter thickness for replacement.

PBIC2916E

Measuring position (RH bank)

No. 1 CYL.

No. 3 CYL.

No. 5 CYL.

No. 5 cylinder at

compression TDC

EXH

×

INT

×

Measuring position (LH bank)

No. 2 CYL.

No. 4 CYL.

No. 6 CYL.

No. 5 cylinder at

compression TDC

INT

×

EXH

×

PBIC2056E

KBIA0057E

CAMSHAFT VALVE CLEARANCE

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• Thickness of new valve lifter can be identified by stamp marks

on the reverse side (inside the cylinder).

Intake

Available thickness of valve lifter: 27 sizes with range 7.88 to 8.40 mm (0.3102 to 0.3307 in) in steps of

0.02 mm (0.0008 in) (when manufactured at factory). Refer to

EM-130, "Standard and Limit"

.

Exhaust

Available thickness of valve lifter: 25 sizes with range 7.88 to 8.36 mm (0.3102 to 0.3291 in) in steps of

0.02 mm (0.0008 in) (when manufactured at factory). Refer to

EM-130, "Standard and Limit"

.

CAUTION:

Install identification letter at the end and top, “U” and “N”, at each of proper positions. (Be care-

ful of mis-installation between intake and exhaust.)

6. Install selected valve lifter.
7. Install camshaft. Refer to

EM-76, "Removal and Installation"

.

8. Instructionly turn crankshaft pulley a few turns.
9. Make sure that the valve clearances for cold engine are within the specifications by referring to the speci-

fied values.

10. Installation of the remaining components is in the reverse order of removal.
11. Start the engine, and check for unusual noise and vibration.

Valve lifter thickness calculation:

t = t

1

+ (C

1

– C

2

)

t

= Valve lifter thickness to be replaced

t

1

= Removed valve lifter thickness

C

1

= Measured valve clearance

C

2

= Standard valve clearance:

Intake

: 0.26 - 0.34 mm (0.010 - 0.013 in)*

Exhaust

: 0.29 - 0.37 mm (0.011 - 0.015 in)*

*: Approximately 20

°C (68°F)

KBIA0119E

Stamp mark

Thickness

788U

7.88 mm (0.3102 in)

790U

7.90 mm (0.3110 in)

·

·

·

·

840U

8.40 mm (0.3307 in)

Stamp mark

Thickness

N788

7.88 mm (0.3102 in)

N790

7.90 mm (0.3110 in)

·

·

·

·

N836

8.36 mm (0.3291 in)

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COMPRESSION PRESSURE

COMPRESSION PRESSURE

Compression Pressure

INFOID:0000000009484449

CHECKING COMPRESSION PRESSURE

1. Warm up engine thoroughly.
2. Release fuel pressure. Refer to

EC-494, "Fuel Pressure Check"

.

3. Disconnect fuel pump fuse to avoid fuel injection during mea-

surement.

4. Remove intake manifold collector. Refer to

EM-25, "Removal and Installation"

.

5. Remove spark plug from each cylinder. Refer to

EM-16, "Removal and Installation"

.

6. Connect engine tachometer (not required in use of CONSULT).
7. Install compression tester with adapter onto spark plug hole.

• Use compression gauge whose pick up end inserted to spark

plug hole is smaller than 20 mm (0.79 in) in diameter. Other-

wise, it may be caught by cylinder head during removal.

8. Turn ignition switch to “START” for cranking. When the gauge pointer stabilizes, read the compression

pressure and engine rpm. Perform these steps to check each cylinder.

Compression pressure:

Unit: kPa (kg/cm

2

, psi) /rpm

CAUTION:

Always use a fully charged battery to obtain specified engine speed.

• If the engine speed is out of the specified range check the battery and recharge as necessary. Check

the engine speed again with the battery properly charged.

BBIA0534E

PBIC0900E

SBIA0533E

Standard

Minimum

Differential limit between cylinders

1,275 (13.0, 185) / 300

981 (10.0, 142) / 300

98 (1.0, 14) / 300

COMPRESSION PRESSURE

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• If some cylinders have low compression pressure, pour a small amount of engine oil into the spark plug

hole of the cylinder to re-check it for compression.

- If the added engine oil improves the compression, piston rings may be worn out or damaged. Check the

piston rings and replace if necessary

- If the compression pressure remains at low level despite the addition of engine oil, the valves may be

malfunctioning. Check the valves for damage. Replace the valve or valve seat accordingly.

• If two adjacent cylinders have respectively low compression pressure and their compression remains

low even after the addition of engine oil, cylinder head gaskets may be leaking, or a valve in adjacent

cylinders may be damaged. Inspect and repair as required.

• If the compression pressure is below the minimum value, check the valve clearances and parts associ-

ated with the combustion chamber (valve, valve seat, piston, piston ring, cylinder bore, cylinder head,

cylinder head gasket). After the checking, measure the compression pressure again.

9. Install the components in the reverse order of removal.
10. Start the engine, and confirm that it runs smoothly.
11. Perform trouble diagnosis. If DTC appears, erase it. Refer to

EC-141, "Description"

.