Rough idle in cold weather

[bluey]

For the past week or so, the Polo has started idling rough only when cold. Dealer said this is probably normal and apparently is a "feature" of emission control of EuroV cars and not unique to VW. He said BMW do it too. to get it diagnosed, have to leave the car at the dealer overnight so they can see it do its thing.

I have read some people describe this as being due to a secondary air injection pump issue. So what's the go??

[Darkhorse Developments]

When the engine is cold at the rpm is high it will feel rough. (yes as per emissions ti heat up catalyst quicker) when the coolant temp reaches 32oc the idle will drop to normal then the engine should run smooth

[zillar32]

What oil are you using? In the cold use 5w40