If you haven't changed out your O2 sensor in a while, I would start there. When fully warm, the exhaust should smell of nothing but hot air. If it doesn't you probably need a tuneup and/or mixture adjustment.

Also heard that a new air filter and oil change can get a borderline car thru. Make sure the engine is full warmed up when you go.

__________________
1985 380SE Blue/Blue - 230,000 miles
2012 Subaru Forester 5-speed
2005 Toyota Sienna
2004 Chrysler Sebring convertible
1999 Toyota Tacoma