Subaru IMPREZA 2004 Service Manual page 8

IGNITION
5) Remove the spark plug cords by pulling the boot,
not cord itself.
6) Remove the spark plugs with spark plug sock-
ets.
B: INSTALLATION
1. RH SIDE
Install in the reverse order of removal.
NOTE:
• For tightening torque, refer to "COMPONENT".
<Ref. to IG(H4SO)-3, COMPONENT, General De-
scription.>
• 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.
NOTE:
• For tightening torque, refer to "COMPONENT".
<Ref. to IG(H4SO)-3, COMPONENT, General De-
scription.>
• 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.
Spark Plug
C: INSPECTION
Check the electrodes and inner and outer ceramic
insulator of plugs, noting the type of deposits and
the degree of electrode erosion.
IG-00021
1) Normal:
Brown to grayish-tan deposits and slight electrode
wear indicates correct spark plug heat range.
IG-00022
2) Carbon fouled:
Dry fluffy carbon deposits on insulator and elec-
trode are mostly caused by slow speed driving in
city, weak ignition, too rich fuel mixture, dirty air
cleaner, etc.
It is advisable to replace with plugs having hotter
heat range.
IG(H4SO)-6
(A)
(B)
(E)
(A) Spark plug gap
(B) Carbon accumulation or wear
(C) Cracks
(D) Damage
(E) Damaged gasket
(C)
(D)
IG-00023
IG-00024
IG-00025