I would imagine you're referencing the '86 model car you own - 17 yrs. old now. Mileage is not always an issue. You could have a bad stem seal in that cyl. as well as a faulty guide or oil ring(piston).

I'd recommend professional analysis. A compression test was suggested - a leak-down test could also prove useful.

If the oil has been changed semi-regularly, I'd bet on the problem being in the head, but again, these things are difficult to analyze over the WEB. Go see a pro if you do not posess the knowledge and have the equipment to analyze.

My 2 cents.