exhaust smell in car

just noticed about a week ago in my 94 grand cherokee that the air conditioning/heat was letting in what smelled like exhaust? why is this?

there are only 2 causes that I can think of, the Catalytic Converter is plugged and need to be replaced, or the EGR Valve/EGR Transduce (control unit) is bad.

might not be exhaust at all. could be that mold problem some have with moisture and plant materials in the evaporator/heater chamber under the dash.

http://home.sc.rr.com/janet/TSB/24-11-97.htm

http://home.sc.rr.com/janet/TSB/24-11-97R.htm

A plugged converter would affect performance and gas mileage. Not sure about the egr transducer but the egr valve would likely affect idle quality and possibly some other performance areas as well.

JD

well ive noticed also within the past week when im sitting in traffic and i let of the brake a little it kinda chugs its not smooth and yesterday when i filled up i got 255 miles with 18.001 gallons which is low 14's but its always been about 15 but i did quite a few times floor it to get infront of people and other times i could tell i was being wasteful, so i think the gas is normal, but under all this take into consideration that its been colder the past week (id say about 40-45 degree average) and also at points ive had stalls or almost when switching from reverse into drive after pulling out of my driveway with the wheel all the way turned (dksob says IAC on that) but thats what my jeep has been like up to date if that gives any clues

but it definatly was not mold or anything, it smelled like exhaust