Dirty plugg???

[imported_JamesL]

Hi guys,
I decided to pull my plugs out yesterday to inspect them. 3 plugs were damp with fuel and reasonably clean but one plug was really dirty and clogged up with a hard white substance.
The motor is and old 1980 85hp V4.
What would cause this?
The reason i pulled the plugs was because the motor was idling rough.
Thanks
James

 

[Joe Reeves]

Re: Dirty plugg???

A hard white substance? Possibly not so white? At any rate, that sounds like either salt buildup or a piston in the eprocess of destroying itself due to pre-ignition. I'd sugest that you remove that cylinder head in order to inspect further. Let us know what you find.