Is there a way to increase the idle speed while the aircon is operating???

while sitting at traffic lights ect. it idles very low with it on and when i go to pull away, it almost stalls..

The carb on your wagon

(I guess this is the car to which you are referring?)

has a high idle assist operated via a diaphragm.

 

This diaphragm is operated by a vacuum control

solenoid valve.

 

When the AC is on the solenoid opens a vacuum path

to the diaphragm and a lever holds the carb linkage

open to offset the drag induced by the compressor.

 

Any of the fore mentioned items may be knackered.

The diaphragm is located to the driverside of the carb

and has a several cm. long lever extending to the carb linkage.