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Use of Car Exhaust Gas Analyzer

One: the role of automobile exhaust gas analyzer: used to analyze the parameters such as CO HC CO2 O2 air-fuel ratio A / F in the exhaust gas to determine whether the mixture is rich or lean, and whether the exhaust emissions meet the standards; Note: When measuring exhaust gas, be warm Locomotive to normal operating temperature.

Correct exhaust emission parameters under normal conditions

①CO is normally 0.012%

Low CO content, indicating the more complete combustion of the combustible mixture;

Under normal circumstances, CO emissions are close to 0%;

If the CO content in the exhaust gas is higher, it means that the mixture is too rich and not completely burned. The possible reasons are the high fuel pressure, the fuel leak from the injector, and the dirty air filter element.


HC is generated when the fuel is not burned or completely burned during the combustion process;

Under normal circumstances, the HC emission of the engine is less than 100ppm; when it is completely burned: between 3-10ppm

When the mixture is too rich, HC emissions will increase;

When the mixture is too lean, such as ignition failure will also lead to increased HC emissions;


CO2 is the product of combustible mixture combustion, and its level reflects the quality of the mixture combustion, that is, the combustion efficiency;

The more completely the combustible mixture is burned, the higher the CO2 reading. When the mixture is fully burned, the CO2 content in the exhaust gas reaches a peak of 13-16%;

When the engine mixture becomes too rich or too lean, the CO2 content will decrease. When the CO2 at the tail of the exhaust pipe is low, the concentration or leanness of the engine mixture should be determined according to the concentration of other emissions.


The content of O2 is a good indicator of the air-fuel ratio of the mixture, and is one of the useful diagnostic data for zui;

If the combustion is normal, only a small amount of unburned O2 is discharged at this time, and when O2 is passed through the catalytic converter, the content of O2 in the exhaust gas is less than 1%;

If the O2 reading is greater than 2%, it means that the mixture is too dilute;

⑤ Air-fuel ratio A / F

A / F is the air-fuel ratio calculated by the analyzer based on the measured HC, O2 and other gases, and this data is the actual response of the current engine air-fuel ratio;

When we are diagnosing the fault of rich and lean mixture, observe this value first;

Normally between 0.9-1.1

Less than 1 is a rich mixture; more than 1 is a lean mixture;

2: Exhaust gas parameters in exhaust gas analysis measured when the mixture is lean

HC: fuel is not completely burned HC rises into> 1.4 is lean O2> 5%

HC is not completely converted to CO2, resulting in reduced CO2 emissions

3: Parameters in the exhaust gas when the mixed gas is concentrated

CO: CO value rises due to incomplete combustion of the mixture

Entering <1 indicates that the mixture is rich

HC: the mixture is not completely burned, causing the HC value to become abnormally large

CO2: the value of CO2 decreases accordingly;

Summary: For example, when we doubt the accuracy of the data in ISTA, we can use the exhaust gas analyzer to accurately measure the current air-fuel ratio status.

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