After changing the oxygen sensor, I feel that the car consumes a lot of gas. Why?

With the new sensor, the trip computer needs to be re-matched. Matching is the throttle opening, fuel injection and exhaust emissions detected by sensors. It will take some time for ECU to adapt after matching. In other words, why do some cars feel like waste oil after washing the throttle and nozzle? Because there will be carbon deposits on the throttle nozzle when it is not washed, and there will be some during normal maintenance. For example, after cleaning, the throttle opening is 90% or the fuel injection amount is 90%. Compared with the 60% fuel injection or throttle opening that you haven't cleaned before, the fuel consumption is definitely different. In the past, the opening was 2/3, but now it is 3/3, so the fuel injection and air intake will obviously increase 1/3, so waste oil is used.

Oxygen sensor:

Oxygen sensor is an important component in an engine that uses a three-way catalytic converter to reduce exhaust pollution. Once the air-fuel ratio of the mixture deviates from the theoretical air-fuel ratio, the purification ability of the three-way catalyst for CO, HC and NOx will drop sharply. Therefore, an oxygen sensor is installed in the exhaust pipe to detect the oxygen concentration in the exhaust gas and send a feedback signal to the ECU, and then the ECU controls the increase or decrease of the fuel injection quantity of the injector, so as to control the air-fuel ratio of the mixed gas near the theoretical value.

Function:

In order to obtain high exhaust gas purification rate and reduce the components such as (CO) carbon monoxide, (HC) hydrocarbons and (nitrogen oxides) nitrogen oxides in exhaust gas, EFI vehicles must use three-way catalytic converters. However, in order to effectively use the three-way catalytic converter, it is necessary to accurately control the air-fuel ratio so that it is always close to the theoretical air-fuel ratio. The catalyst is usually installed between the exhaust manifold and the muffler. The oxygen sensor has a characteristic that its output voltage suddenly changes near the theoretical air-fuel ratio (14.7: 1). This characteristic is used to detect the oxygen concentration in the exhaust gas and feed it back to the computer to control the air-fuel ratio. When the actual air-fuel ratio becomes higher, the oxygen concentration in the exhaust gas increases, and the oxygen sensor informs the ECU of the lean state of the mixture (small electromotive force: 0 volts). When the air-fuel ratio is lower than the theoretical air-fuel ratio, the oxygen concentration in the exhaust gas decreases, and the state of the oxygen sensor (large electromotive force: 1V) is notified to the ECU computer.

ECU judges whether the air-fuel ratio is low or high according to the electromotive force difference from the oxygen sensor, and controls the fuel injection duration accordingly. However, if the oxygen transmitter fails and the output electromotive force is abnormal, the ECU computer cannot accurately control the air-fuel ratio. Therefore, the oxygen sensor can also make up for the air-fuel ratio error caused by the wear of the mechanical and other parts of the EFI system. It can be said that it is the only "intelligent" sensor in the EFI system.

The function of the sensor is to determine whether there is excess oxygen in the exhaust gas after engine combustion, that is, oxygen content, and convert the oxygen content into voltage signal and transmit it to the engine computer, so that the engine can realize closed-loop control with excess air coefficient as the goal; Ensure that the three-way catalytic converter has the maximum conversion efficiency for hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOX) in the exhaust gas, and convert and purify the discharged pollutants to the greatest extent.