Volkswagen 's new boss began trying to pull the embattled carmaker out of the wreckage of a pollution test rigging scandal Saturday, as the United States and Switzerland halted the sale of the group's new diesel cars. The 62-year-old former Porsche chief Matthias Mueller was tapped Friday to replace Martin Winterkorn, who resigned over stunning revelations by US environmental authorities that the German carmaker had fitted some of its diesel cars with software capable of cheating environmental tests.