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General and misc questions about car engines

Q: When replacing the spark plugs, they were coated with oil. When I unscrewed them, I think that oil flowed into the cylinder. Did this damage anything like my catalytic converter?

A: Oil in the spark plug wells is due to bad valve cover gasket seal, particularly the (usually) separate round gaskets around each spark plug well. Oil will attack the rubber high voltage wire boot over time, and will eventually cause misfire. If you are working on an old car, or a car you know will have a lot of oil in the well, you can carefully suck it out with a syringe attached to a thin tube.

To the best of my knowledge, the oil will be burned in the cylinder before it is pushed out the exhaust valve. This will develop soot, but it should not damage the catalytic converter if it is done just on that seldom occasion. But you should replace the valve cover gasket because it is the cheapest solution.

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Problem: My car is showing an check engine code for a MAF or oxygen sensor failure. The engine produces exhaust that smells.

WARNING WARNING WARNING

Operating your engine with a failed MAF, oxygen sensors, and the like will have the car computer resort to GUESSING AND WILL ALWAYS OPERATE TOO RICH. This will produce poisonous exhaust, but more importantly IT WILL DUMP UNBURNED GASOLINE IN THE EXHAUST, WHERE IT WILL BE BURNED BY THE CATALYTIC CONVERTER, MAKING THE CATALYTIC CONVERTER TOO HOT. CONTINUING TO OPERATE THE CAR ON A RICH MIXTURE WILL IRREVERSIBLY RUIN THE VERY EXPENSIVE CATALYTIC CONVERTER.

 

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