Is It Normal for the Exhaust to Smell Bad When the Car Just Starts?
2 Answers
It is normal for the exhaust to smell bad when the car just starts. This is due to incomplete combustion of the air-fuel mixture during a cold start. Reasons for the bad smell when starting: When the car just starts, it is in a cold start condition. The car's computer, based on signals from sensors such as coolant temperature and intake air temperature, determines that the car is in a cold state and thus injects more fuel. Additionally, the catalytic converter has not reached its optimal temperature, resulting in poor treatment of the exhaust gases. This leads to the presence of large amounts of sulfur compounds, carbon oxides, and nitrogen oxides in the exhaust, causing the noticeable smell during startup. Automobile exhaust pollutants: The exhaust gases produced during car use contain hundreds of different compounds, including pollutants such as solid suspended particles, carbon monoxide, carbon dioxide, hydrocarbons, nitrogen oxides, lead, and sulfur oxides. Exhaust gases not only directly harm human health but also have a profound impact on the environment in which we live.
I also used to worry about this when I first bought my car. It's actually quite common for exhaust fumes to smell unpleasant right after starting the car, especially in winter when the engine hasn't warmed up yet. In cold conditions, combustion efficiency is lower, releasing more unburned fuel odors due to sludge and carbon buildup inside the engine. The catalytic converter takes a few minutes to heat up and become effective; otherwise, exhaust purification isn't optimal. After driving this car for three years, I've noticed the smell is more noticeable when temperatures drop below 10°C, but it disappears after a few minutes of driving as the engine warms up. However, if abnormal smells persist—like a rotten egg sulfur odor or strong gasoline fumes—it could indicate a faulty catalytic converter or fuel leak, requiring immediate inspection. Regular maintenance can prevent this. I clean carbon deposits every six months to minimize such odor issues. In short, temporary unpleasant smells are normal, but prolonged issues shouldn't be ignored.
