09 CM871 ticking and surging at cold start

[09KWW900]

At a cold start my 09 CM871 has started making a ticking sound, followed by a slight rough idle with some slight surging or lurching with the tick. Once it warms up everything is fine, no performance issues at all. Is anybody familiar with this and can pinpoint the issue? I have a video of it making the sound but can't seem to upload it here. Any info would be greatly appreciated.