Focus mk1 1.6 very rough idle

[V6todayEVmanana]

The focus never had a smooth idle but recently the car is really shuddering.

Whilst moving the car is super smooth and the engine revs great.

Any idea what I should be checking/replacing.

Its a 2001 75k petrol.

Thanks

[njw1]

The idle air control valve, it's a silver cylindrical thingy on the inlet manifold.