When the outside temperature changes from high to low, the engine jitter changes from small to large. What is the reason?

The automobile uses the intake pressure sensor, and ECU estimates the intake air volume according to the negative pressure data obtained by the pressure sensor located behind the throttle, so as to judge the fuel supply and make the engine get a reasonable air-fuel ratio. Unlike many cars with air flow meters, cars with pressure sensors don't really know how much "air" they get. At the same altitude, the atmospheric pressure is basically the same, but the same pressure has different air density at different temperatures, with low density when it is hot and high density when it is cold. In other words, cold weather makes the air dense, and the air density directly affects the oxygen content. When the weather is hot, the air-fuel ratio will be thicker and the car will be more stable. In cold weather, when the oxygen content is pressurized and the fuel supply is constant, lean combustion will occur, which is weak and will produce certain knocking, so the car will shake. When ECU detects knocking, it will adjust the fuel supply in the range of +-7%, but when the oxygen sensor fails, the adjustment function will be invalid. The jitter will be very obvious.