1995 Mazda Millenia 1995 mazda millenia stalls when idleing

i have a 1995 mazda millenia with a 2.3L emgine and i have been experiancing stalling. when i turn on my car it runs fine but after i put the car into drive and then come to a stop it stalls. i have just recently replaced the alternator, and had the transmission rebuilt. also when i turn on the car a lot of white smoke comes out of the exhaust.