Exhaust fumes

You need a live person to look at the exhaust system and see what is wrong. To start, look at the tail pipe to see if where it ends has moved. Pipes that exit to the side, behind a tire, are prone to bending forward when they hit something while backing up. If a pipe is cracked underneath, you should hear excessive noise, and there has to be a hole or open window where the fumes are coming in. If the leak is toward the front or near the engine, fumes can be drawn into the fresh air intake for the heater. You will smell the fumes coming out of the vents. Check the rubber seal that runs along the rear edge of the hood. That may have pulled loose or has gaps worn in it.