Slight misfire, air pump?

[Argenta]

Hi’ya!
My M has developed a very slight misfire at cold starts, which has gotten a little worse this year. It goes away when the secondary air pump / ”smogpump” shuts down - after I’d say 30sec - then it runs perfectly.
I’ve checked compression, all coils & plugs are all new.

Any guess? Seems to be related to the air-pump, IMHO.

 

[Mr Tidy]

My MC does this as well.

I recently read about E46s having the same issue on m3cutters and the consensus seemed to be either the secondary air pump or possibly a failed throttle position sensor.

Link here:- https://forums.m3cutters.co.uk/threads/m3-e46-kangaroos.255165/#post-3446215

 

[Argenta]

Thanx, ok it doesn’t ”kangaroo” actually I haven’t noticed anything weird driving it. Its on first 30sec of tickover you can feel the engine rumble about, which stops when the pump stops.

 

[Mr Tidy]

I think "kangaroo" might not have been the best description! I'd describe it more as stuttering.