autobox vauxhall?

I got a vectra-b 98/99 with autobox. the problem is that car will sit and rev nice in P, N but when you engage the rest of the gears R, D, 1, 2 as soon as you come of the brake the engine will stall.

if you give it a good rev as you come of the brake you can get the car going but it doesn't change gears properly.


ANY IDEAS would be great as it doing my head in