When the 1.6K Series engine is started (from hot or cold), occasionally (1-2 a month) the engine fails to idle properly. On bad occasions, it will not idle at all and simply stalls. Othertimes, it hunts down to 400-500 RPM before recovering. Heavy electrical load (HRW, lights etc) exacerbates the problem. Restarting from ignition off rectifies the fault. However, starting from stalled does not. Have had an (expensive) Rover diagnostics check which indicated that everything was OK. However, the car was not exhibiting the fault when the check was performed. Any ideas?

Yeah...the diagnostic check wouldn't uncover any problems - you would be aware of a fault as the PGMFi Warning lamp would flag up..

The base idle speed needs resetting, that's all....you could even do this yourself if you have a screwdriver and tachometer handy and you have some mechanical skills (No, you can't use the rev counter, it's not that accurate..)

Thanks for the info on the base idle speed. I'll leave this one to the dealer!

Why is it that the problem only occurs intermittently and sometimes worse than others?

Could be an ECU related problem Steve...given the intermittant nature of the fault.

I'd try all adjustments possible before condemning the ECU but I'd expect your dealer check to have encompassed all these beforehand :)