If the unpleasant smell is penetrating into the car when the engine is running while the engine is running, it may be possible to exhaust the exhaust gas into the passenger compartment. We need to try to turn on the air conditioner, which activates the air recycling system, and check if there's any unpleasant smell.
If it is active in motion, it may be caused by heating the exhaust components as soon as possible. It is necessary to inspect the sealant of the cover of the windshield through which the smell of the engine compartment can penetrate into the occupant compartment.