Ok saga still ongoing and have done further investigation. Car exhibits the following
- starts from cold ok and idles at fast idle , gradually adjusting idle speed down to 950rpm
- once engine has some warmth the idle speed then drops almost to stall then recovers and does this about three or four times before the idle stabilizes, sometimes the car stalls. The car does this every 45s or so.
- on the road the car drives and pulls well but exhibits the surging idle issue if you sit at lights etc for a period of time. Car sometimes stalls when you dip the clutch
reluctant to start hot , when it does it runs rough initially then clears if you rev it with evidence of black smoke from exhaust until it clears itself
have done following so far
- co levels are around 5%
- exhaust smells like its running rich
- plugs are black when removed
- changed ICV ..... no effect
- checked spec of CHT / AFM all seems ok to Bentley manual.
- cleaned AFM very little dirt or deposits visible, flap moves freely
- bridged the CHT loom connector , no effect , idle continues its cycles of falling rising every 45s or so.
I am fairly clear it’s running rich maybe choking itself which system tries to cope with trying to stop it stalling.
Any further ideas advice now I have done further investigation