Ignition (H4DOTC Engine): Diagnosis Subaru Impreza GD/GC/GG рестайлинг 2

INSPECTION

Check the electrodes and inner and outer ceramic insulator of plugs, noting the type of deposits and the degree of electrode erosion.

Identifying Spark Plug Gap. Scheme 23

Scheme 24

Scheme 25

Scheme 26

1. Normal: Brown to grayish-tan deposits and slight electrode wear indicates correct spark plug heat range. (Scheme 24): Identifying Normal
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 and dirty air cleaner, etc. (Scheme 25): Identifying Carbon Fouled
3. Oil fouled: Wet black deposits show oil entrance into combustion chamber through worn rings and pistons or excessive clearance between valve guides and stems. (Scheme 26): Identifying Oil Fouled
4. Overheating

White or light gray insulator with black or brown spots and bluish burnt electrodes indicates engine overheating. Moreover, the appearance results from incorrect ignition timing, loose spark plugs, wrong selection of fuel, hotter range plug, etc.

Identifying Overheating. Scheme 27

For inspection, refer to the following. < Ref. to IGNITION CONTROL SYSTEM , Diagnostics for Engine Starting Failure. >