What should I do if the tail gas of Nissan Teana 2.4V6 engine is too strong in 2006?

This is mainly because this model is older. After the mileage of this engine is increased, the deterioration of engine performance will lead to poor combustion of the engine, and this phenomenon will occur. In addition, after more kilometers, the engine produces more carbon deposits, which will also occur. It is necessary to clean the throttle and nozzle, replace the spark plug, clean the three-way catalyst, and check that the engine cylinder has more carbon deposits, and it also needs to be cleaned. You also need to check the data flow of the air intake sensor and the oxygen sensor with a computer to see if there is any problem. If there is any problem, it needs to be checked and cleaned.