Subaru Legacy (2005 year). Manual - part 420

IG(H6DO)-3

IGNITION

General Description

C: CAUTION

• Wear work clothing, including a cap, protective
goggles, and protective shoes during operation.
• 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.
• Be careful not to burn yourself, because each
part on the vehicle is hot after running.
• 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 electrical connectors of
sensors or units, be sure to disconnect the ground
cable from battery.

IG(H6DO)-4

IGNITION

Spark Plug

2. Spark Plug

A: REMOVAL

CAUTION:
All spark plugs installed on an engine must be 
of the same heat range.

Spark plug: 

NGK: ILFR6B

1. RH SIDE

1) Remove the collector cover.
2) Disconnect the ground cable from battery.

3) Remove the air cleaner case.
<Ref. to IN(H6DO)-5, REMOVAL, Air Cleaner
Case.>
4) Remove the bracket.
5) Disconnect the connector from ignition coil.
6) Remove the ignition coil.

NOTE:
Turn the #5 ignition coil to remove it. 

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

2. LH SIDE

1) Remove the collector cover.
2) Remove the battery and battery carrier.
3) Remove the bracket.
4) Disconnect the connector from ignition coil.
5) Remove the ignition coil.

NOTE:
Turn the #6 ignition coil to remove it. 

(A) Bracket

(B) Connector

IN-00203

IG-02004

(B)

(A)

(A) Ratchet handle

(B) Extension bar

(C) Universal joint

(D) Spark plug socket

(A) Bracket

(B) Connector

IG-02005

(D)

(C)

(B)

(B)

(A)

IG-02011

IG-02006

(A)

(B)

IG(H6DO)-5

IGNITION

Spark Plug

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

B: INSTALLATION

1. RH SIDE

Install in the reverse order of removal.

Tightening torque (Spark plug):

21 N

⋅

m (2.1 kgf-m, 15.2 ft-lb)

Tightening torque (Ignition coil):

16 N

⋅

m (1.6 kgf-m, 11.7 ft-lb)

NOTE:
The above torque should be only applied to new
spark plugs without oil on their threads.
In case their threads are lubricated, the torque
should be reduced by approx. 1/3 of the specified
torque in order to avoid over-stressing.

2. LH SIDE

Install in the reverse order of removal.

Tightening torque (Spark plug):

21 N

⋅

m (2.1 kgf-m, 15.2 ft-lb)

Tightening torque (Ignition coil):

16 N

⋅

m (1.6 kgf-m, 11.7 ft-lb)

NOTE:
The above torque should be only applied to new
spark plugs without oil on their threads.
In case their threads are lubricated, the torque
should be reduced by approx. 1/3 of the specified
torque in order to avoid over-stressing.

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.

(A) Ratchet handle

(B) Extension bar

(C) Universal joint

(D) Spark plug socket

IG-02007

(D)

(C)

(B)

(B)

(A)

IG-02011

(A) Spark plug gap

(B) Carbon accumulation or wear

(C) Crack

(D) Damage

(E) Damaged gasket

IG-00010

(A)

(B)

(C)

(D)

(E)

IG-00011

IG(H6DO)-6

IGNITION

Spark Plug

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, dirty air
cleaner, etc.

3) Oil fouled:
Wet black deposits show excessive oil entrance
into combustion chamber through worn rings and
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. Moreover, those appearance also re-
sults from incorrect ignition timing, loose spark
plugs, wrong selection of fuel, etc.

D: ADJUSTMENT

Clean the spark plugs using a wire brush.
Clean and remove the carbon or oxide deposits.
But do not wear away ceramic insulator at this time.
If deposits are too stubborn, replace the spark
plugs.
After cleaning the spark plugs, correct the spark
plug gap using a gap gauge.

NOTE:
Do not use a plug cleaner because the spark plugs
are applied with iridium tip.

Spark plug gap L:

0.7 — 0.8 mm (0.028 — 0.031 in)

IG-00012

IG-00013

IG-00014

IG-02035

L