Hi, I have a Chevrolet Caprice with a 305 4 barrel carburetor and I have oil on just one of my spark plugs!
This particular plug seems to always have oil on it and will get corroded the worst in a short time (3 weeks). The car also seems to misfire on the highway doing about 65 mph. It will seem as an explosion occurs at this speed. I think the problems are directly related but not sure. My knowledge is not this deeply involved. If the problems are related or not what can I do to help fix it?
I suspect the cylinder you are having problems with is the back cylinders.
It sounds as if motor oil is fouling out these plugs!
You said in three weeks it fouls out this "one plug". The repair may be as simple as removing your "Rocker Box" or “Valve Cover” and cleaning the oil drain passages.
What MAY be happening is "sludge build up" has stopped or slowed the oil return from the cylinder heads. So as the car runs, oil gets pumped to the top of the engine and it gets "sucked in" around the valve guide seals.
The symptom of this is a "crusty" white ash deposits on the spark plugs and the car will "smoke" at idle.
The good news is that this can be fixed in one day by most shops. The bad news is finding a shop that wants to do this messy job!
If this is the problem you will need to change your oil more often and make sure your thermostat is the right temperature.
When they do this work they must be careful and not allow the sludge and trash to get left in the engine. If this is allowed to happen this can clog up your oil pump suction screen and tear up your engine.
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