A task force of Japan’s Environment Agency recommended yesterday that owners of old, heavily polluting cars be tapped for higher taxes and that those driving low-emission vehicles get tax reductions. The task force had initially intended to raise taxes on most cars but then limited its plan, in part because of pressure from automakers. Under the current proposal, only 400,000 of the nation’s 70 million vehicles would be hit by the tax change, a number so small that it would have practically no effect on reducing air pollution, some analysts said.