idle control valve and carbon build up?

If it is running rich maybe this has lead to a carbon build up meaning the valve isn't functioning?

Mates cossie used to suffer, unplugg it and it ran fine, but then when started from cold it would cut out as there was no choke iirc? Cleaned it all out and it was fine for a time.

Also had a pug with the same problem, unplugged the idle control valve and rev dropped to normal.