Subaru Legacy IV (2008 year). Manual - part 93

IG(H4SO)-3

General Description

IGNITION

C: CAUTION

• Wear appropriate work clothing, including a cap,
protective goggles and protective shoes when per-
forming any work.
• Remove contamination including dirt and corro-
sion before removal, installation or disassembly.
• Keep the disassembled parts in order and pro-
tect them from dust and dirt.
• Before removal, installation or disassembly, be
sure to clarify the failure. Avoid unnecessary re-
moval, installation, disassembly and replacement.
• Vehicle components are extremely hot after driv-
ing. Be wary of receiving burns from heated parts.
• Be sure to tighten fasteners including bolts and
nuts to the specified torque.
• Place shop jacks or rigid racks at the specified
points.
• Before disconnecting connectors of sensors or
units, be sure to disconnect the ground cable from
the battery.

IG(H4SO)-4

Spark Plug

IGNITION

2. Spark Plug

A: REMOVAL

Spark plug:

Refer to “SPECIFICATION” for the spark 
plug. <Ref. to IG(H4SO)-2, SPECIFICATION, 
General Description.>

1. RH SIDE

1) Disconnect the ground cable from battery.

2) Remove the air cleaner case. <Ref. to
IN(H4SO)-5, REMOVAL, Air Cleaner Case.>
3) Remove the spark plug cords by pulling the boot.
(Do not pull the cord itself.)

4) Remove the spark plug with a spark plug socket.

2. LH SIDE

1) Remove the battery. <Ref. to SC(H4SO)-20,
REMOVAL, Battery.>
2) Remove the spark plug cords by pulling the boot.
(Do not pull the cord itself.)

3) Remove the spark plug with a spark plug socket.

B: INSTALLATION

1. RH SIDE

Install in the reverse order of removal.

Tightening torque:

21 N·m (2.1 kgf-m, 15.5 ft-lb)

2. LH SIDE

Install in the reverse order of removal.

Tightening torque:

21 N·m (2.1 kgf-m, 15.5 ft-lb)

IN-00203

IG-00017

IG-00018

IG-02049

IG-00022

IG(H4SO)-5

Spark Plug

IGNITION

C: INSPECTION

Check the electrodes and inner and outer ceramic
insulator of plugs, noting the type of deposits and
the degree of electrode erosion.

1) Normal:
Brown to grayish-tan deposits and slight electrode
wear indicate correct spark plug heat range.

2) Carbon fouled:
Dry fluffy carbon deposits on insulator and elec-
trode are mostly caused by slow speed driving in
the city, weak ignition, too rich fuel mixture and dirty
air cleaner.

3) Oil fouled:
Wet black deposits show oil entrance into the com-
bustion chamber through worn rings or pistons, or
excessive clearance between valve guides and
stems.

4) Overheating:
White or light gray insulator with black or brown
spots and bluish burnt electrodes indicate engine
overheating, incorrect ignition timing, wrong selec-
tion of fuel, and loose spark plugs.

D: ADJUSTMENT

Clean spark plugs with a nylon brush, etc. Clean
and remove the carbon or oxide deposits. If depos-
its are too stubborn, replace the spark plugs. After
cleaning the spark plugs, measure the spark plug
gap using a gap gauge.

NOTE:
• Never use plug cleaner.
• Do not use metal brush or it will wear insulator.

Spark plug gap L:

1.0 — 1.1 mm (0.039 — 0.043 in)

(A) Spark plug gap

(B) Carbon accumulation or wear

(C) Cracks

(D) Damage

(E) Damaged gasket

IG-00010

(A)

(B)

(C)

(D)

(E)

IG-00011

IG-00012

IG-00013

IG-00014

IG-02035

L

IG(H4SO)-6

Ignition Coil and Ignitor Assembly

IGNITION

3. Ignition Coil and Ignitor 

Assembly

A: REMOVAL

1) Disconnect the ground cable from battery.

2) Disconnect the spark plug cords from ignition
coil and ignitor assembly.

3) Disconnect the connector (A) from the ignition
coil and ignitor assembly.
4) Remove the bolt (B) which secures the ignition
coil and ignitor assembly to the intake manifold.

B: INSTALLATION

Install in the reverse order of removal.

Tightening torque:

8 N·m (0.8 kgf-m, 5.9 ft-lb)

CAUTION:
Connect the spark plug cords to correct posi-
tions. Failure to do so will damage the unit.

C: INSPECTION

Check the secondary coil resistance using a tester.
Replace if defective.

CAUTION:
• If the resistance is extremely low, it indicates
the presence of a short-circuit.
• Ignitor is integrated with the coil. Therefore
the resistance of primary side coil cannot be
measured.

Specified resistance:

[Secondary side]

Between (A) and (B)

11.2 k

:r

15%

Between (C) and (D)

11.2 k

:r

15%

IN-00203

IG-02064

IG-02065

(A)

(B)

(B)

IG-02066

(D)

(B)

(C)

(A)