IACV code

[andy-m]

I was getting an ECL for the idle air control valve and sometimes when I go down hill and off the gas for any length of time, the ECL would come on and not go off unless I punched the clutch and let it idle for a sec.
Also, when I stopped in traffic, sometimes the idle would be a little low but would be cured by blipping the throttle.

So, I pulled the IACV off today and used some carb cleaner. it didnt seem that bad, a little carbon deposit which came off easy and everything was free moving.
Once cleaned up, I re-fitted it and went for a spin. Going down hill and off the gas, I still get the ECL come on as before but the intimittant low idle when I stop has gone.

Any ideas what could make it still throw an ECL for the IACV ?