I had the same problem w/ my 92 EX station wagon when I bought it 6 years ago. I fixed it by replacing the rubber valve cover gasket and the rubber grommet spark plug gaskets. The parts cost less than $30. Even the new gaskets will leak if you do not get them perfectly fitted. I had to do it twice. Warning: Over tightening the nuts and bolts will damage the gasket and same problem will persist.