Outer Limits 4x4 Board

Has anyone experienced an erractic idle with a 3F carby motor and fixed the problem? My car intermittently on both petrol and has has a hugely erratic idle. Normal idle is around 800rpm, but today to keep the car from stalling at the lights I had to apply the choke and the idle was quickly jumping around from 400rpm all the way upto ~1500rpm. Take off from lights remove chock and all is fine, next set of lights and it idles normally.

This problem seems to come and go every few months but I have not been able to track it down. I was thinking its possible something to do with the vacuum secondaries on the stock carby?

My old mans 75 troopy with a 3F did the same, found the wire to the fuel soleniod thing on the side of the carby was a bad connection. With it disconnected, the idle was almost non-existant. Fixed the wiring and all good again. Worth a look into.