I had a 1993 Civic DX with the same problem. It was the head gasket. I sold the car for little to nothing because I didn't have the time, tools, or skills to repair it. The cylinder head replacement kit costs $119.00 from Auto Zone. Keep a close eye on your oil and coolant levels, and make sure the coolant isn't leaking into the oil. If it is, you must fix the problem, or the engine will be damaged beyond repair. Good luck with it.