Subaru IMPREZA GD 2007 Series Manual page 2346

asieps_tobira_IM_US.book 5 ページ ２０１２年１月１７日 火曜日 午後３時４８分
C: INSPECTION
Check the electrodes and inner and outer ceramic
insulator of plugs, noting the type of deposits and
the degree of electrode erosion.
(E)
(B)
(A)
(A) Spark plug gap
(B) Carbon accumulation or wear
(C) Crack
(D) Damage
(E) Damaged gasket
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.
Spark Plug
3) Oil fouled:
Wet black deposits show oil entrance into the com-
bustion chamber through worn rings and excessive
clearance between valve guides and stems.
(C)
(D)
IG-02010
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 up the spark plug using nylon brush or equiv-
alent.
Clean and remove the carbon or oxide deposits.
IG-00011
If deposits are too stubborn, replace the spark
plugs. After cleaning the spark plugs, measure the
spark plug gap using a gap gauge.
NOTE:
• Never use a plug cleaner.
• Never use a metal brush because it makes insu-
lator worn.
Spark plug gap L:
IG-00012
IG(H4DOTC)-5
0.7 — 0.8 mm (0.028 — 0.031 in)
IGNITION
IG-00013
IG-00014
L
IG-00091