Rough idle

[dermotbell]

Hi all,
Last couple of days in Scotland before I head back to the land of sun and dust, and the cars developed a niggle.
It starts well, idles fine when cold, and performs well generally, but when she's hot the idle drops down to 500rpm and sometimes drops below and recovers to 500 and sometimes drops below and doesn't recover. Interestingly when I start her cold and run I garage to hot she doesn't seem to have this problem, really only hits when she's been on a run.
I know CAM angle sensor causes rough running but I thought this was all the time and under acceleration, and that if the base timing needed adjusting it would not be running a good hot idle when warmed in garage?
Any thoughts?
PS my elanscan interface has been misplaced so I have no data

[Brit-Car-Nut]

First, look for a vacuum leak around any place in the engine bay where you might have bumped a hose off.

[dermotbell]

Ok, just waiting for torrential rain to stop.
Surprised that if it was vacuum that it wouldn't affect it all the time?

[Brit-Car-Nut]

When the engine is "cold", the ECM compensates with a richer mixture and a leak isn't as obvious. Once it warms up, the mixture will be lean if a vacuum line is off - or worse, if it is a hose that goes to a sensor which doesn't know what is then going on.