Subaru Legacy IV (2008 year). Manual - part 491

ME(H6DO)-90

Engine Trouble in General

MECHANICAL

7. After burning in exhaust 
system

Engine control system <Ref. to EN(H6DO)(diag)-2, Basic Diagnostic Procedure.>

A

Intake system

Loosened or cracked intake duct

C

Loosened or cracked PCV hose

C

Loosened or cracked vacuum hose

B

Defective PCV valve

B

Loosened oil filler cap

C

Timing chain

Defective timing

B

Compression

Incorrect valve clearance

B

Loosened spark plug or defective gasket

C

Loosened cylinder head bolt or defective gasket

C

Improper valve sealing

B

Defective valve stem

C

Worn or broken valve spring

C

Worn or stuck piston rings, cylinder and piston

C

Incorrect valve timing

A

Trouble of valve lifter

C

Trouble of valve lifter. (In case noise occurs with valve 
moving. Or the harness involved to oil switching sole-
noid valve, variable valve lift diagnosis oil pressure 
switch and variable valve lift has trouble in a past.)

B

Lubrication system

Incorrect oil pressure

C

Cooling system

Over-cooling

C

Others

Evaporative emission control system malfunction

C

8. Knocking

Engine control system <Ref. to EN(H6DO)(diag)-2, Basic Diagnostic Procedure.>

A

Intake system

Loosened oil filler cap

B

Timing chain

Defective timing

B

Compression

Incorrect valve clearance

C

Incorrect valve timing

B

Trouble of valve lifter

C

Trouble of valve lifter. (In case noise occurs with valve 
moving. Or the harness involved to oil switching sole-
noid valve, variable valve lift diagnosis oil pressure 
switch and variable valve lift has trouble in a past.)

B

Cooling system

Over-heating

A

9. Excessive engine oil con-
sumption

Intake system

Loosened or cracked PCV hose

A

Defective PCV valve

B

Loosened oil filler cap

C

Compression

Defective valve stem

A

Worn or stuck piston rings, cylinder and piston

A

Lubrication system

Loosened oil pump attaching bolts and defective gas-
ket

B

Defective oil filter O-ring

B

Defective crankshaft oil seal

B

Defective rocker cover gasket

B

Loosened oil drain plug or defective gasket

B

Loosened oil pan fitting bolts or defective oil pan

B

Symptoms

Problem parts etc.

Possible cause

RANK

ME(H6DO)-91

Engine Trouble in General

MECHANICAL

10. Excessive fuel consump-
tion

Engine control system <Ref. to EN(H6DO)(diag)-2, Basic Diagnostic Procedure.>

A

Intake system

Dirty air cleaner element

A

Timing chain

Defective timing

B

Compression

Incorrect valve clearance

B

Loosened spark plug or defective gasket

C

Loosened cylinder head bolt or defective gasket

C

Improper valve sealing

B

Defective valve stem

C

Worn or broken valve spring

C

Worn or stuck piston rings, cylinder and piston

B

Incorrect valve timing

B

Trouble of valve lifter

C

Trouble of valve lifter. (In case noise occurs with valve 
moving. Or the harness involved to oil switching sole-
noid valve, variable valve lift diagnosis oil pressure 
switch and variable valve lift has trouble in a past.)

B

Lubrication system

Incorrect oil pressure

C

Cooling system

Over-cooling

C

Symptoms

Problem parts etc.

Possible cause

RANK

ME(H6DO)-92

Engine Noise

MECHANICAL

29.Engine Noise

A: INSPECTION

NOTE*)
When disconnecting the fuel injector connector, the malfunction indicator light illuminates and DTC is stored in ECM memory.
Therefore, perform the Clear Memory Mode <Ref. to EN(H6DO)(diag)-52, OPERATION, Clear Memory Mode.> and Inspection
Mode <Ref. to EN(H6DO)(diag)-44, PROCEDURE, Inspection Mode.> after connecting the fuel injector connector.

Type of sound

Condition

Possible cause

Regular clicking sound

Sound increases as engine 
speed increases.

• Valve mechanism is defective.
• Incorrect valve clearance
• Worn camshaft
• Broken valve spring
• Trouble of valve lifter

Heavy and dull clank

Oil pressure is low.

• Worn crankshaft main bearing
• Worn connecting rod bearing (large end)

Oil pressure is normal.

Damaged engine mounting

High-pitched clank

Sound is noticeable when 
accelerating with an overload 
condition.

• Ignition timing advanced
• Accumulation of carbon inside combustion chamber
• Wrong heat range of spark plug
• Improper octane value of gasoline

Clank when engine speed is 
between 1,000 and 2,000 rpm.

Noise is reduced when fuel 
injector connector of noisy cyl-
inder is disconnected. 
(NOTE*)

• Worn crankshaft main bearing
• Worn connecting rod bearing (large end)

Knocking sound when engine 
is operating under idling speed 
and engine is warm

Noise is reduced when fuel 
injector connector of noisy cyl-
inder is disconnected. 
(NOTE*)

• Worn cylinder liner and piston ring
• Broken or stuck piston ring
• Worn piston pin and hole at piston end of connecting rod

Sound is not reduced if each 
fuel injector connector is dis-
connected in turn. (NOTE*)

• Unusually worn valve lifter
• Worn cam gear
• Worn camshaft journal bore in cylinder head

Squeaky sound

 — 

Insufficient generator lubrication

Rubbing sound

 — 

Poor contact of generator brush and rotor

Gear scream when starting 
engine

 — 

• Defective ignition starter switch
• Worn gear and starter pinion

Sound like polishing glass with 
a dry cloth

 — 

• Loose drive belt
• Defective water pump shaft

Hissing sound

 — 

• Insufficient compression
• Air leakage in air intake system, hose, connection or manifold

Timing chain noise

 — 

• Loose timing chain
• Timing chain contacting with adjacent part

Valve noise

 — 

• Incorrect valve clearance
• Trouble of valve lifter

EX(H6DO)-2

General Description

EXHAUST

1. General Description

A: COMPONENT

EX-02374

T2

T4

T5

T1

T1

T3

T3

T4

T4

(18)

(12)

(11)

(10)

(8)

T6

T6

(20)

(21)

(22)

(23)

(25)

(24)

(17)

(24)

(24)

(24)

(26)

(24)

(25)

(16)

(26)

(13)

(15)

(19)

(14)

T3

(6)

(7)

(5)

T3

(4)

(3)

(1)

(2)

(9)