harmonic balancer
my sister 2000 ford windstar van engine still shakes evan after had the heads taken off and tested, new head gaskets, new intake gaskets, new plugs & wires, new motor mounts, compretion to the cylinders are good , replaced I A C .
i had a 91 thunder bird with same simler problem and sold it for $500. dollars and the person that bought it told me a week later it was the harmonic balancer , could the problem with the van be the same.