Most connections / joints between parts have a gasket to prevent leaks.
So a failed gasket is a typical cause of leaks, including where the exhaust pipes connects to the exhaust manifold.
Leak in exhaust system?
Exhaust leak, failed oxygen sensor, failed catalytic converter.
Leak in the exhaust system?
Blown head gasket and/or cracked head.
The fumes are most likely coming from an exhaust leak. The leak could be at the converter, or somewhere else in the exhaust system.
Leak in exhaust system perhaps exhaust manifold being sucked in through air intake (grid at lower end of windshield)
Usually this is a vacuum leak. Can also be a leak in the exhaust system.
Exhaust gasses are escaping through a hole or rotted section of exhaust system
There can be several causes for the service emissions systems light to come on in a Ford Escape. The light can indicate an 02 sensor is out or it can indicate an exhaust leak.
The injection system has a tiny air leak that causes the system to not work correctly until the air is purged from the injectors. Look for a tiny fuel leak near and injector or an increase in engine oil level that will show fuel contamination in the oil
Fixing a leak depends on where the leak is and the severity. An exhaust connection could be loose or a gasket is bad. If there is a hole in a pipe there is a possibility that the hole can be welded, taking care to stay away from fuel lines or anything flammable.
Either a slack connection or a hole.