Chim irratic tick over.

[Mike Hawthorn]

Any suggestions. Due to an irratic tick over for some time I did the normal checks and took the stepper motor out of the system. Blanked off the hose and up'ed the idle screw 8 turns to give me a 8-9K idle. OK in most respects but still lost idle some times for no reason. I then took the plug off the stepper. This was better and most the time ok.(I'm guessing the ECU gets info it can't process despite the stepper being disconnected?) I've now fitted a new stepper motor and all is fine but just every now and again it'll lose it's idle then when I restart idle at 1500 ish.
Any suggestions?
I notice that what looks like the water side of the choke system is un-used. Is this normal?