A Dongtian Nissan New Teana car with a mileage of about 25 thousand km, equipped with VQ25 DE engine and REOF10A continuously variable transmission (VQ25). The user reports the exhaust pipe to smoke the blue smoke. Because the user reflects the failure after maintenance, the author thinks that the oil is too much added in maintenance, but when the oil level is checked, it is found that the oil level is below the middle line of the oil scale, indicating that the oil is less. Check the maintenance records of the user and find that the last maintenance mileage is 9500km, and the current mileage of the vehicle has reached 21 thousand km, exceeding the normal maintenance mileage of more than 5000 km. The crankcase forced ventilation valve is connected to the hose to be removed. It is found that the oil is flowing out. It is preliminarily judged that the oil is oxidized after the mileage is overdue, and the oil sludge like oxide has blocked the oil and gas separation in the valve chamber cover. So the air intake pipe was removed and it was found that there was also a lot of oil in the intake pipe, which indicated that there was a problem in the oil and gas separation system on the valve chamber cover. Continue to remove the hood of the engine valve chamber. It is found that there are many oil oxides and sludge in the valve chamber cover.