The head gasket is blown.
Sounds like your oxygen sensor may be out.
If the car heat has a fresh air setting, then it could be drawing air from outside of the vehicle. The fumes are most likely coming from a problem under the hood.
must be a leak cant think of any other way check all joints and manifold incl lambda sensor failing that cracked cylinder head from exhaust valve but i wudda thought the running would be impaired
I would be more worried about the foods I eat, do some research on msg! Accidents. Cigarettes and exhaust fumes take years to kill you; some accidents will kill you immediately.
exhaust leak or a possible fuel line leak
One reason would be exhaust fumes may enter the cabin area.
Running "Rich" Dirty air filter? Carb. Probably needs adjusting
it would have 2 b a exaust leak or the little hose going 2 your breather element isn't attached properlyAnswercould be your cat as well Damaged or restricted exhaust system components; Restricted, loose or burned out muffler.straight out, go to an exhaust shop. u have a leaky exhaustAnswerNo who, but what. All internal combustion engines emit exhaust fumes.
valve guides or valve guide seals or piston rings. in colder weather?
Blown headgasket.
leaking past the rings