You don't mention what you found but most common would be oil spilt on exhaust during oil/filter change. A/C brings on rad fans which would circulate smell.
98 Mystique LS v6 atx 110,000km
97 Contour LX v6 atx 125,000km
stock CD on LS, cass on LX
spoiler, tinted windows on LS only
4 wheel discs on LX only
All other available options on both
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