Volvo: check engine light, passing emissions, oil spill

Question
i am looking into buying a 1998 v70 turbo wagon.  the check engine light is on and the salesman says it has something to do with a "rich oil mix" or something like that.  he thinks it was caused by an oil spill during a routine oil change that flooded one of the spark plugs.  is this possible, and if so is it expensive to fix? we really like the car but are unsure about volvo due to lack of experience. thank you for your reply-ben

Answer
Ben,
If some oil was indeed spilled and it shorted out a spark plug, it would set a misfire code. With cleaning of the oil reading and clearing the codes car should be fine. Now if the dealer wants to sell the car he should have this work done before doing so. I think that I would insist that this be done and that if needed should be tested for passing emissions.