Subaru 2009 IMPREZA Service Manual page 1218

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B: INSTALLATION

Install in the reverse order of removal.

Tightening torque (Spark plug):

21 N·m (2.1 kgf-m, 15.5 ft-lb)

Tightening torque (Ignition coil):

16 N·m (1.6 kgf-m, 11.8 ft-lb)

Install in the reverse order of removal.

Tightening torque (Spark plug):

21 N·m (2.1 kgf-m, 15.5 ft-lb)

Tightening torque (Ignition coil):

16 N·m (1.6 kgf-m, 11.8 ft-lb)

Tightening torque (Air pump duct):

9 N·m (0.9 kgf-m, 6.6 ft-lb)

C: INSPECTION

Check the electrodes and inner and outer ceramic

insulator of plugs, noting the type of deposits and

the degree of electrode erosion.

(A) Spark plug gap

(B) Carbon accumulation or wear

(E) Damaged gasket

Brown to grayish-tan deposits and slight electrode

wear indicate correct spark plug heat range.

IG(H4DOTC)-5

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 oil entrance into combus-

tion chamber through worn rings or increased

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, improper fu-

el, or loose spark plugs.