А так не пробовали
function TForm4.FDnnection(SQLwe:string): string;
begin
FDConnection1.Params.DriverID:='MSAcc';
FDConnection1.Params.Database:=Form2.PathBaseEdit.Text;
FDConnection1.Connected:=true;
FDQuery1.SQL.Add(SQLwe);
FDQuery1.Active:=true;
end;