Volvo Repair: Engine seems to be cutting, volvo specialist, s40 volvo

Question
My 2000 S40 Volvo 1.8 Automatic's engine seems to cut when the vehicle is stationery or moving at low speed, resulting in a surging or juddery movement. This worsens when the air con is switched on.
Also, why is my aircon fan always on?

Answer
Phineas, This is something that has to be taken to your Volvo dealer or Volvo Specialist shop.  The can needs to be scanned to find out what is wrong. These newer cars are hard to diagnose without looking at them.  Which fan are you talking about?  The interior fan or exterior fan?  Roger