What Causes Overly Rich Air-Fuel Mixture in Cars?

[PiperLee]

Causes of overly rich air-fuel mixture in cars: 1. Excessive fuel level; 2. Malfunction of vacuum economizer; 3. Clogged main air jet emulsion tube; 4. Blocked air filter. During troubleshooting, check if the choke valve is fully open. After the engine stalls, observe the main nozzle from the carburetor opening. If fuel drips are present, it indicates the float chamber fuel level is too high and should be adjusted to the specified range. If the air filter is clogged, immediate cleaning and unclogging of the filter is required. The air-fuel mixture refers to the combination of fuel and air, typically gasoline, diesel and air. However, with advancements in automotive technology and fuel diversity, modern mixtures also include combinations with various combustible gases such as natural gas, methane, coal gas, ethanol, and methanol.