Why is the ford fusion making a loud engine noise?

Your Ford Fusion making a loud engine noise could be caused by a failing or d***y sensor. It can send incorrect data, resulting in too much or too little fuel going to the engine. This can result in a rough running engine that is louder than normal. A bad or d***y spark plugs can also cause a loud noise. Bad spark plugs can cause the vehicle to mIS Fire which will make it run louder. I would start with changing the spark plugs. As a rule of thumb, You should replace Your spark plugs in intervals of every 20,000 to 40,000 miles.