What does 'car feels sluggish' mean?

[McDeclan]

"Sluggish" refers to the process where a car takes a relatively long time to accelerate from a standstill to a certain speed, making the acceleration feel overly gradual and resulting in a perception of poor performance, fatigue, and sluggishness. Generally, this means the car lacks sufficient power or has low torque, leading to difficult acceleration. The main reasons why a car becomes increasingly sluggish are as follows: 1. Damaged air flow meter: The air flow meter, or air flow sensor, detects the amount of air intake and converts it into an electrical signal sent to the Engine Control Unit (ECU). Based on the optimal air-fuel ratio, the ECU indirectly determines the amount of fuel to inject. If the air flow sensor or its circuit malfunctions, the ECU will not receive the correct air intake signal, preventing normal fuel control. If this results in an overly lean air-fuel mixture, it can lead to insufficient engine power output. 2. Oxygen sensor failure: Modern cars are equipped with two oxygen sensors on the exhaust pipe—one before the three-way catalytic converter and one after. The front oxygen sensor detects the oxygen content in the exhaust, and the ECU adjusts the fuel injection amount and calculates the ignition timing based on this signal. The rear oxygen sensor primarily monitors the performance of the three-way catalytic converter and assists in fuel injection control. Therefore, if the oxygen sensor is damaged, or its connector is faulty or loose, it can lead to an overly lean mixture, reducing power performance. 3. Spark plug carbon buildup: The varying quality of fuel on the market and congested urban traffic make it easy for spark plugs to accumulate carbon deposits. Carbon buildup on spark plugs can cause poor engine performance, including difficulties in starting, unstable idling, poor acceleration, backfiring during rapid acceleration, excessive exhaust emissions, and increased fuel consumption.