I have pretty crap knowledge as the micra is the first car I have eve had and therefore worked on. So this may be wrong!
On the air filter housing there is a switch you can flick between summer and winter. I think winter mode just means air is drawn in from the exhaust system where it is warmer making the engine run better. In summer the outside air is already warm so this isnt needed.
I dont know what is considered as warm outside though. This time of year ok?
