Forester S F4-2.5L DOHC (1998)
Spark Plug: Service and Repair
Cleaning and Regapping
CLEANING AND REGAPPING
Clean spark plugs in a sand blast type cleaner. Avoid excessive blasting. Clean and remove carbon or oxide deposits, but do not wear away porcelain.
If deposits are too stubborn, discard plugs. After cleaning spark plugs, recondition firing surface of electrodes with file. Then correct the spark plug gap
using a gap gauge.