Horrible Smell through vents when using Outside air not Inside

Hi guys,

Really hope you might be able to help me.

I have recently got my partner a 2007 Micra K12 1.2. When the vents are on outside air source the car really stinks. I am not entirely sure what the smell is or how to describe it apart from maybe a musty cheesy pongy sensation. This issue is not there when on internal recirc. I've never smelt this smell before.

To try and find what was causing this I had the internal pollen filter out and hoovered the casing out. It wasn't a particularly dirty filter. I ran the car on internal only without the pollen filter nor it's cover plate in for many days and noticed no smells.

I have replaced the pollen filter with a Bosch carbon activated one however the smell is still there.

At first I thought it might the oil strewn all over the inside of the bonnet. I have cleaned this away and it's not that. You can notice the smell if you sniff near the windscreen cowling through either side of the air vents. I have had this cowling off previously and it didn't look dirty of anything like that, however access is very difficult.

Any ideas what I could look for? I was going to get a air vent cleaner, however am I correct to assume if the vents are not smelly on the internal re-circ then this won't really make much of a difference.

I asked Nissan dealer if they could tell me where abouts the air enters the car from below the cowling so I could try and spray a cleaner in, however their "Master Technician" didn't know.
Usually more a problem of cars with aircon, you do get a kind of antiseptic fumigation kit that cleans all the bacteria from the pipe work.
Usually more a problem of cars with aircon, you do get a kind of antiseptic fumigation kit that cleans all the bacteria from the pipe work.

Hi, the car does have air-con, however the system isn't charged so it doesn't cool at present.

I have seen those cleaners you speak of. I could do with spraying from the engine bay, unless it's possible to remove the pollen filter again and spray in to the inlet. Do you happen to know which side of the car the air is taken in from. Left or Right when looking in the engine bay?

Usually it's the passenger side since the fan usually sits up at the scuttle panel, and more room on the passenger side. Cans say for sureon the micra as I've never take the fan out.

The air is taken in up at the scuttle panel, should be no direct access of air from the engine bay.
Cheers guys. I've already changed previously the filter :)

What I have done is got some disinfectant aerosol and sprayed it through both of the vents on the windscreen cowling whilst having the vent blower on full. I used the full can then let the engine run for 30 minutes continuing with blower at full and hot. I also sprayed some of it directly in to the interior vents.

The car blowers now do not smell rank, but of some flowery smell. Hopefully this has worked as driving it today doesn't show any nasty smells at moment.

I also emptied the washer bottle and then filled with white vinegar left for 30 minutes then ran through nozzles. After i flushed with water - just in case it's the windscreen washer fluid that is also contributing.