Infiniti QX56 (Z62). Manual — part 644

EM-16

< BASIC INSPECTION >

COMPRESSION PRESSURE

COMPRESSION PRESSURE

Inspection

INFOID:0000000006289521

1.

Warm up engine thoroughly. Then, stop it.

2.

Release fuel pressure. Refer to

EC-153, "Work Procedure"

.

CAUTION:

If CONSULT-III is not used to release fuel pressure leave the fuel pump fuse disconnected until
step 7.

3.

Remove fuel pump fuse in IPDM E/R.
NOTE:
• For the fuse number, refer to

EC-114, "Wiring Diagram"

.

• For the fuse arrangement, refer to

PG-143, "Fuse, Connector and Terminal Arrangement"

.

4.

Remove engine cover. Refer to

EM-25, "Exploded View"

.

5.

Remove ignition coil and spark plug from each cylinder. Refer to

EM-29, "Exploded View"

.

6.

Connect engine tachometer (not required in use of CONSULT-III).

7.

Install the compression tester with Tool [SST: EG15050500 (J-
45402)] into the spark plug hole.

8.

Measure compression pressure using compression gauge connected with flexible type adapter (commer-
cial service tool).

9.

With accelerator pedal fully depressed, turn ignition switch to “START” for cranking. When the gauge
pointer stabilizes, read the compression pressure and the engine rpm. Perform these steps to check each
cylinder.

CAUTION:

• Measure a six-cylinder under the same conditions since a measurement depends on measure-

ment conditions (engine water temperature, etc.).

• Always use a fully changed battery to obtain the specified engine speed.
• If the engine speed is out of the specified range, check battery liquid for proper gravity. Check the

engine speed again with normal battery gravity. Refer to

PG-159, "How to Handle Battery"

.

• If compression pressure is below the minimum value, check valve clearances and parts associated with

combustion chamber (valve, valve seat, piston, piston ring, cylinder bore, cylinder head, cylinder head
gasket). After checking, measure compression pressure again.

• If a cylinder has 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 pis-

ton rings and replace if necessary. Refer to

EM-107, "Disassembly and Assembly"

.

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

functioning. Check valves for damage. Replace valve or valve seat accordingly. Refer to

EM-107, "Dis-

assembly and Assembly"

.

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

low even after the addition of engine oil, cylinder head gaskets are leaking. In such a case, replace cyl-
inder head gaskets. Refer to

EM-87, "Removal and Installation"

.

10. After inspection is completed, install removed parts.
11. Start the engine, and check that the engine runs smoothly.

WBIA0605E

Compression pressure

: Refer to

EM-132, "General Specification"

.

COMPRESSION PRESSURE

EM-17

< BASIC INSPECTION >

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12. Perform trouble diagnosis. If DTC appears, erase it. Refer to

EC-161, "Description"

.

EM-18

< SYMPTOM DIAGNOSIS >

NOISE, VIBRATION AND HARSHNESS (NVH) TROUBLESHOOTING

SYMPTOM DIAGNOSIS

NOISE, VIBRATION AND HARSHNESS (NVH) TROUBLESHOOTING

NVH Troubleshooting - Engine Noise

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JPBIA3483GB

NOISE, VIBRATION AND HARSHNESS (NVH) TROUBLESHOOTING

EM-19

< SYMPTOM DIAGNOSIS >

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Use the Chart Below to Help You Find the Cause of the Symptom

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1.

Locate the area where noise occurs.

2.

Confirm the type of noise.

3.

Specify the operating condition of the engine.

4.

Check specified noise source.

If necessary, repair or replace these parts.

A: Closely related

B: Related

C: Sometimes related

—: Not related

Location

of noise

Type of

noise

Operating condition of engine

Source of

noise

Check item

Refer-

ence page

Before

warm-

up

After

warm-

up

When

start-

ing

When

idling

When

racing

While

driving

Top of en-
gine
Rocker
cover
Cylinder
head

Ticking or
clicking

C

A

—

A

B

—

Tappet
noise

Valve clearance

EM-12

Rattle

C

A

—

A

B

C

Camshaft
bearing
noise

Camshaft runout
Camshaft journal oil
clearance

EM-77

Crank-
shaft pul-
ley
Cylinder
block
(Side of
engine)
Oil pan

Slap or
knock

—

A

—

B

B

—

Piston pin
noise

Piston to piston pin oil
clearance
Connecting rod bushing
oil clearance

EM-115

Slap or
rap

A

—

—

B

B

A

Piston
slap noise

Piston to cylinder bore
clearance
Piston ring side clear-
ance
Piston ring end gap
Connecting rod bend
and torsion

EM-115

Knock

A

B

C

B

B

B

Connect-
ing rod
bearing
noise

Connecting rod bushing
oil clearance
Connecting rod bearing
oil clearance

EM-115

Knock

A

B

—

A

B

C

Main bear-
ing noise

Main bearing oil clear-
ance
Crankshaft runout

EM-115

Front of
engine
Timing
chain case

Tapping or
ticking

A

A

—

B

B

B

Timing
chain and
timing
chain ten-
sioner
noise

Timing chain cracks
and wears
Timing chain tensioner
operation

EM-72

Front of
engine

Squeak-
ing or fizz-
ing

A

B

—

B

—

C

Drive belts
(Sticking
or slip-
ping)

Drive belts deflection

EM-20

Creaking

A

B

A

B

A

B

Drive belts
(Slipping)

Idler pulley bearing op-
eration

Squall
Creak

A

B

—

B

A

B

Water
pump
noise

Water pump operation

CO-19