1.5 auto stalls when put in gear

Hi everyone recently my 1.5 auto (1982) started to stall when i slowed down or came to a stop. My mate had a look at it for me he said it had an airlock in the fuel system, he fixed it and also put a new fuel filter in. It idles fine in neutral but it still stalls as soon as i put it into drive. He then suggested the revs need to be brought up by adjusting the accelerator cable at the transmission side as the cable was slack on the gear selector. As he tried to adjust it the nylon thread snapped… I'm now stuck as i can't find an accelerator cable anywhere as they don't make them any more.
  I would really appreciate it if anyone can give me some advice on whether a new accelerator cable might stop it from stalling if adjusted correctly and also if anyone knows where to get one from. Thank you for reading this and i apologise for my technical ignorance! Ryan