What I do on my 84 500 SEL. Just in front of the air intake is a fire wall that has a rubber seal on top of it. Pull the seal off where it passes the air intake grills. Take 3 Bounce dryer sheets and lay them over the air intake, overlapping each other, with the front edge of the sheets on top of the firewall. Push the rubber seal back on so it holds the sheets in place. The sheets act as filters and help with the smell in the car.
Is it a fix for the problem? No. Does it help some? Yes.

Paul

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84 500 SEL (307,xxx miles)