My 2006 Vauxhall Zafira 1.6 petrol is making an odd noise when idling at low revs. It is not continious, only when the engine is warm and every 30 - 40 seconds.
It's hard to describe, it does not sound mechanical, and it does not sound like trapped air somewhere in the system. When it makes the noise you can hear the engine dip slightly.
Any ideas? Where I am there is no easy access to a good mechanic!