engine stalls

Hello everyone. I own a ford ranger 145k, 1986, 2.3L 4 cyl, auto. It starts real good without any problem but when I swift from park to reverse or drive, it stalls and engine quits. To get it going forward I have to step on the gas pedal quickly as soon as I swift to drive. Sometimes I step on the brake pedal all the way to the floor and seems to help from stalling, but lately that doesn't help anymore. I replaced the plugs, points and Distributor cap but it didn't changed. What's the next step that I need to do. Please help