Under what circumstances does a car operate at idle speed?

[StBrandon]

When waiting at a red light, the car is stationary and the accelerator is not pressed, at which point the engine operates at idle speed. Here is relevant information: 1. Idle speed operation: Idle speed occurs when the engine and wheels are in a power transmission state with the throttle valve closed. Air enters the engine through the throttle valve gap and the idle speed adjustment channel bypassing the throttle valve. 2. Prolonged idling can easily lead to carbon deposits: During idling, the car operates in a rich fuel injection state. This means that when idling, the throttle opening is very small, and the injector sprays highly concentrated fuel to maintain engine operation. Therefore, idling itself is more likely to cause carbon buildup compared to when the car is moving or at high speeds. Extended idling will definitely result in more severe engine carbon deposits.

[LaEmilio]

When driving in traffic congestion, the car often idles. I frequently encounter this scenario during rush hours, especially in downtown areas or near highway entrances, where traffic moves slowly. There's no need to press the accelerator; the engine can maintain idle speed to inch forward bit by bit. When waiting at a traffic light that's about to change, I also use idle speed to move slowly to avoid sudden stalling and causing trouble. Additionally, when circling a parking lot looking for a spot, controlling the speed is essential to avoid hitting obstacles, and idling is very useful. However, this consumes a lot of fuel and isn't very environmentally friendly, as emissions increase significantly. Therefore, I recommend minimizing such situations and using public transportation more to alleviate congestion. Moreover, manual transmission cars can have issues starting on slopes, and idling can stabilize the car to prevent stalling. But for older cars, prolonged idling may lead to carbon buildup, affecting longevity, so regular maintenance is essential.

[AriannaRose]

As a new driver who just got my license, I often use idle speed driving to ensure safety on steep slopes or narrow roads. For example, when starting on a steep slope with a manual transmission, it's easy to stall, but crawling slowly at idle speed is much simpler. Or when turning in narrow alleys, I worry about hitting things if the speed is too fast, so driving at idle speed gives me better control. On rainy days when the road is slippery, rapid acceleration might cause skidding and accidents, so driving at idle speed keeps the tires firmly gripping the ground, which is more reassuring. When waiting for traffic lights to change, I also rely on idle speed to prevent the car from rolling back or suddenly stopping, which could cause a rear-end collision. Although this consumes a bit more fuel, it's better than having an accident. During practice, I combine idle speed with actual conditions to hone my control skills and develop good habits, which can reduce unnecessary use and protect the engine.

[McDante]

I usually prioritize eco-friendly driving habits, minimizing idling to reduce exhaust emissions. However, there are specific situations where idling is necessary, such as briefly inching forward between traffic light changes to prevent congestion or avoiding engine stalling, which could cause greater pollution from restarting. On snowy or slippery roads, controlling speed through idling prevents sudden acceleration and skidding for safer driving. While convenient, idling consumes about 20% more fuel than normal driving, increasing carbon emissions. Therefore, I generally plan routes in advance to avoid congested areas or turn off the engine at traffic lights. In the long run, reducing idling helps the planet, but safety comes first—using it appropriately ensures smooth journeys when needed.