Subaru Legacy IV (2008 year). Manual - part 490

ME(H6DO)-86

Engine Trouble in General

MECHANICAL

3) Initial combustion occurs.

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

A

Intake system

Defective intake manifold gasket

B

Defective throttle body gasket

B

Fuel line

Defective fuel pump and relay

C

Clogged fuel line

C

Lack of or insufficient fuel

B

Timing chain

Trouble

B

Defective timing

B

Compression

Incorrect valve clearance

C

Loosened spark plug or defective gasket

C

Loosened cylinder head bolt or defective gasket

C

Improper valve sealing

C

Defective valve stem

C

Worn or broken valve spring

B

Worn or stuck piston rings, cylinder and piston

C

Incorrect valve timing

B

Improper engine oil (low viscosity)

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

4) Engine stalls after initial 
combustion.

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

A

Intake system

Loosened or cracked intake duct

B

Loosened or cracked PCV hose

C

Loosened or cracked vacuum hose

C

Defective intake manifold gasket

B

Defective throttle body gasket

B

Dirty air cleaner element

C

Fuel line

Clogged fuel line

C

Lack of or insufficient fuel

B

Timing chain

Trouble

B

Defective timing

B

Compression

Incorrect valve clearance

C

Loosened spark plug or defective gasket

C

Loosened cylinder head bolt or defective gasket

C

Improper valve sealing

C

Defective valve stem

C

Worn or broken valve spring

B

Worn or stuck piston rings, cylinder and piston

C

Incorrect valve timing

B

Improper engine oil (low viscosity)

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

Symptoms

Problem parts etc.

Possible cause

RANK

ME(H6DO)-87

Engine Trouble in General

MECHANICAL

2. Rough idle and engine 
stall

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

A

Intake system

Loosened or cracked intake duct

A

Loosened or cracked PCV hose

A

Loosened or cracked vacuum hose

A

Defective intake manifold gasket

B

Defective throttle body gasket

B

Defective PCV valve

C

Loosened oil filler cap

B

Dirty air cleaner element

C

Fuel line

Defective fuel pump and relay

C

Clogged fuel line

C

Lack of or insufficient fuel

B

Timing chain

Defective timing

C

Compression

Incorrect valve clearance

B

Loosened spark plug or defective gasket

B

Loosened cylinder head bolt or defective gasket

B

Improper valve sealing

B

Defective valve stem

C

Worn or broken valve spring

B

Worn or stuck piston rings, cylinder and piston

B

Incorrect valve timing

A

Improper engine oil (low viscosity)

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

B

Defective rocker cover gasket

C

Cooling system

Over-heating

C

Others

Evaporative emission control system malfunction

A

Stuck or damaged throttle valve

B

Symptoms

Problem parts etc.

Possible cause

RANK

ME(H6DO)-88

Engine Trouble in General

MECHANICAL

3. Low output, hesitation and 
poor acceleration

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

A

Intake system

Loosened or cracked intake duct

A

Loosened or cracked PCV hose

A

Loosened or cracked vacuum hose

B

Defective intake manifold gasket

B

Defective throttle body gasket

B

Defective PCV valve

B

Loosened oil filler cap

B

Dirty air cleaner element

A

Fuel line

Defective fuel pump and relay

B

Clogged fuel line

B

Lack of or insufficient fuel

C

Timing chain

Defective timing

B

Compression

Incorrect valve clearance

B

Loosened spark plug or defective gasket

B

Loosened cylinder head bolt or defective gasket

B

Improper valve sealing

B

Defective valve stem

C

Worn or broken valve spring

B

Worn or stuck piston rings, cylinder and piston

C

Incorrect valve timing

A

Improper engine oil (low viscosity)

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

B

Cooling system

Over-heating

C

Over-cooling

C

Others

Evaporative emission control system malfunction

A

Symptoms

Problem parts etc.

Possible cause

RANK

ME(H6DO)-89

Engine Trouble in General

MECHANICAL

4. Surging

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

A

Intake system

Loosened or cracked intake duct

A

Loosened or cracked PCV hose

A

Loosened or cracked vacuum hose

A

Defective intake manifold gasket

B

Defective throttle body gasket

B

Defective PCV valve

B

Loosened oil filler cap

B

Dirty air cleaner element

B

Fuel line

Defective fuel pump and relay

B

Clogged fuel line

B

Lack of or insufficient fuel

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

C

Defective valve stem

C

Worn or broken valve spring

C

Worn or stuck piston rings, cylinder and piston

C

Incorrect valve timing

A

Improper engine oil (low viscosity)

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

B

Others

Evaporative emission control system malfunction

C

5. Engine does not return to 
idle.

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

A

Intake system

Loosened or cracked vacuum hose

A

Others

Stuck or damaged throttle valve

A

6. Dieseling (Run-on)

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

A

Cooling system

Over-heating

B

Others

Evaporative emission control system malfunction

B

Symptoms

Problem parts etc.

Possible cause

RANK