The reasons for the bad smell in the Focus are as follows: 1. Air filter causing odor: Many owners report that when the air conditioning is turned on, a sour and musty smell blows in, which is very unpleasant, but this condition usually eases after a while. In fact, this odor is a sign that the air filter needs to be replaced. The air conditioning system has been decomposed by bacteria, leading to mold, and replacing the air filter can alleviate the smell. 2. Evaporator causing odor: If the smell persists after replacing the air filter, the issue likely lies with the evaporator. Mold inside the evaporator is the culprit, and simply replacing the air filter won't solve the problem. In this case, cleaning the evaporator and air conditioning ducts is necessary. Some repair shops may also offer an additional service called "interior sauna," with effectiveness depending on the thoroughness of the cleaning. 3. Smoking causing interior odor: Owners who frequently smoke in the car may not notice the smell (due to adaptation), but others, especially women, find it very noticeable and unpleasant. To eliminate this odor, a thorough cleaning of the car's interior, including the air conditioning and upholstery, is required. 4. Trunk clutter causing odor: Owners who store various items in the trunk, especially eggs and meat, may encounter strong odors. Broken eggs or thawing frozen meat can leave liquids in the trunk, which over time produce a pungent smell. Special treatment at a car wash is needed to resolve this issue. 5. Pungent plastic smell inside the car: A burnt plastic smell that appears when the car is running but disappears when the car is turned off and cools down is likely caused by a plastic bag stuck to the exhaust pipe. The high temperature of the exhaust pipe melts the plastic, releasing the odor into the car. Removing the melted plastic from the exhaust pipe is the only way to eliminate this smell.
