Attached are pictures of my Civic spark plugs, which have not been taken out for a while. The first one is not covered by deposit, the last 3 are the same and all covered by a bit hard deposit. Please tell what cause this kind of deposit (Close-up 3)? Thanks

Note: The first plug has oil leak down to the thread due to the bad valve cover seal

Civic 91 CX HB, 1.5L, Auto,

http://cid-e63342b401399125.photos.live.com/self.aspx/Pictures

http://cid-e63342b401399125.photos.live.com/self.aspx/Pictures

Likely ash deposits. Solutions range from changing gasoline brands to replacing valve guide seals.

TxGreaseMonkey, thanks for your help with the diagnosis.

Since not all 4 spark plugs have deposit so should I concentrate on the oil path?

The car do have problems of running a bit rough at starting and consuming oil (the car has some white smoke at the tail pipe, but no external oil leak), but any chance oil cause that almost white ash deposit? Any chance coolant cause this almost white ash deposit (not much coolant lost)? Thanks

White smoke is almost invariably caused by coolant leaking into the combustion chamber--think blown head gasket or cracked head. The leak my be affecting only one cylinder.