How to Determine if the Car's Air-Fuel Mixture is Too Rich?
3 Answers
Automobile air-fuel mixture refers to the combination of fuel (such as gasoline or diesel) and air. There are four main methods to determine if a car's air-fuel mixture is too rich. Below is a detailed introduction to these four methods: 1. Presence of fuel leakage: When there is fuel leakage at the carburetor throttle shaft or gasket, it indicates that the car's air-fuel mixture concentration is too high. 2. Decreased engine power: When the air-fuel mixture is excessively rich, the engine's power decreases while fuel consumption increases. 3. Carbon deposits on electrodes: When removing the spark plug, if wet gasoline and significant carbon deposits are observed on the electrode surface, this indicates an overly rich air-fuel mixture. 4. Unstable engine idle: Decreased engine power accompanied by irregular abnormal noises from the muffler also signifies an excessively rich air-fuel mixture.
When you feel the car engine running as if it's stuck, with unstable and shaky idling, it might be due to a rich fuel mixture. As someone who drives frequently, I've noticed the most obvious sign is black smoke from the exhaust, accompanied by a burnt smell—this usually indicates unburned excess fuel. A sudden spike in fuel consumption is another red flag; for example, if a full tank used to last 400 km but now only gets you 300 km, pay attention. Additionally, check the spark plugs. If the ceramic tip is covered in thick black soot instead of the normal light tan color, it means there's too much fuel clogging them. I recommend regularly using an OBD scanner to check for trouble codes, such as P0172, which can pinpoint the issue. Don’t delay, or you might damage the catalytic converter. Over time, this can also harm the engine's lifespan.
Having driven for decades, I know that when the air-fuel mixture is too rich, the car staggers like a drunkard, with unstable idle speed during startup—the RPM jumps up and down erratically. Thick black smoke spews from the exhaust pipe, resembling coal dust from a chimney, leaving black stains on the rear of the car that smear when touched. If you remove the spark plugs and find them coated with oil and soot instead of being clean and shiny, it means there's too much unburned fuel. I remember fixing an old car in my younger days—ignoring this issue caused fuel consumption to skyrocket, costing me hundreds extra every month. Nowadays, I check it myself at roadside shops using a simple air-fuel ratio tester inserted into the exhaust pipe. If the readings show it's too lean, that's a clear sign to get it repaired promptly.
