Mazda Motor Corp.'s North American operations said it is recalling more than 5,700 cars in the United States to fix emission problems. The Japanese automaker, one third of which is owned by the world's No. 2 automaker Ford Motor Co. , is recalling about 3,504 1995-model MX-6 and 2,274 1995-model 626 sedans equipped with V6 engines and five-speed manual transmissions for the addition of a vent kit to the emission control system.