Hello!
 I have a Impreza 2000 AT. When car is cold when I'm not driving the engine works properly. When I start driving in "Drive"  mode till I touch brakes the engine turning off. It's like the automatic transmittion don't allow to switch gear. I changed sparkling plugs, MAF, iddle ect., nothing helps. 
 When engine warms up, everything works perfectly - engine, automatic transmittion...
  
 May be someone had similar problem and have any suggestion whet to do?!
  
  
  
 Yours sincerely -
  
 Edvib
  
  
  
 P.S. Sorry for my English!