How much does the part cost to fix the emission system

Thanks for the question. It is impossible to answer the question without knowing exactly what is wrong with the car. Have you had it checked out? Also if you are smelling fumes, have you had the exhaust system inspected?

Hello, you'll never know until you find out what component(s) need(s) to be replaced. A diagnostic test is required. If you are smelling fumes of exhaust (keeping in mind that carbon monoxide gas is entirely odorless...so I assume you mean exhaust fumes), I would recommend having a thorough inspection of your exhaust system from the engine through the back of the vehicle. If you have a leak, this could enter the cabin, causing fumes. If you have a check engine light on, you'll have to have that tested also -- could be related or a separate concern. Good luck.