search for posts on how to clean the throttle body inside. I did mine today, it wouldnt idle either, I thought the throttle cable had gone slack but it was a small amout of crap built up at the edges of the butterfly valve and causing it to stall. The idle air gap is only about 0.5mm so blocks easy with sooty fumes from the breather pipes over the years.
You have to take the TB right off not just clean it from one side, and make sure the inner walls are spotless as well as the edges of the butterfly disc. Use petrol, WD40 or Wynns carb cleaner. Believe me it will work.
If it starts with the throttle open slightly and revs but wont idle then it has to be the TB butterfly or the ISV (idle stabilisation valve) if fitted.