Subaru XT 1988 Service Manual page 1207

6-1
ENGINE ELECTRICAL SYSTEM
Spark Plug
DESCRIPTION
1.0 - 1.1
mm
(0.039 - 0.043
in)
A9-163
Fig. 63
The spark plugs are project type, having 14 mm (0.551 in)
threads and 1.0 to 1.1 mm (0.039 to 0.043 in) gap.
All spark plugs installed on an engine, must be of the same
heat range.
Applicable model Spark plug
NGK:
BPR6ES-11
(or BPR5ES-l1, BPR7ES-11)
U.S.A.
NIPPONDENSO:
W20EPR-U11
(or W16EPR-Ul1, W22EPR-U11)
CHAMPION:
RN9YC4 (or RN11YC4)
Canada
CHAMPION:
RN9YC-4 (or RN11YC-4)
REMOVAL AND INSTALLATION
1) Remove spark plug cords by pulling boot, not cord itself.
2) Remove spark plugs.
3) When installing spark plugs on cylinder head, use spark
pi ug wrench.
Tightening torque (Spark plug):
20 - 29 N'm (2 - 3 kg-m. 14 - 22 ft·lb)
26
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 approximately 1/3 of the specified torque in order
to avoid their over-stressing.
4) Connect spark plug cords.
INSPECTION
O1eck electrodes and inner and outer procelains of plugs,
noting the type of deposits and the degree of electrode
erosion.
1) Normal
Brown to grayish-tan deposits and sl ight electrode wear
indicate correct spark plug heat range.
A9·164
Fig.
64
2) Carbon fouled
Dry fluffy carbon deposits on insulator and electrode 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.
A9-165
Fig. 65