1989 Lincoln Town Car steam coming from exhust

Do a pressure test, and compression leakdown test, these cars had issues with intake manifold gaskets, and corrosion at the corners of the heads and manifold, a pressure test will show the leaks, you can also remove the spark plugs and see if any are discolored or wet. If it turns out to be the more severe head gasket problem, you can try this if you don't want to replace the gaskets.