I smell exhaust when I put the fan on

Last week, I finally gave in and had the dealer change my 2001 Civic HX’s cabin air filter (among other things bundled in $700 of “maintenance”) to get rid of the funkiness that I smelled when I put the fan on.

Now I’ve got a totally different problem . . . where when I put the fan on and when I’m stopped at a stoplight, I seem to be able to smell exhaust (presumably) from the vehicle in front of me. On more open road, or with the vent closed, I don’t smell it as much (or maybe I just got used to it).

Is this normal? Maybe there’s a “break in” period for the new air filter (or maybe it isn’t the problem at all)? I’m pretty sensitive to smells (I can smell my little dog’s poop from across the house) – but I don’t remember the exhaust smell being so bad when the car was new. Is this something I should be worried about?

Any help on this matter would be greatly appreciated!



A new cabin air filter can’t stop particles so small that cause an odor. The old filter may have been so gunked up that it wasn’t allowing much air past it so less air means less odor. The new filter may allow more airflow and with it more odor.

Otherwise you are either are too close to smelly car exhaust, or your own car may have a leaky exhaust. Since your Honda is a 2001 a leaky exhaust is possible and worth having checked out.

I can offer one possible explanation. On my cars, the original factory cabin filters had a layer of paper filter and a layer of carbon fiber. The carbon fiber did not actually remove chemicals and odors (not nearly thick enough to do that), rather it simply smoothed out the spikes in odor, like when you drive past a dead animal on the road, so they were not so noticeable.

The aftermarket filters that I have purchased had the paper layer only. I don’t notice much, if any difference, but I don’t have a very sensitive sniffer.

You need to make sure the source of your smell is not comming from your car (mixture problem,or some type of fluid getting hot or even a exhaust system problem). As for now I am not connecting the dots between replacement of cabin filter and the onset of the smell.