What is the reason for the engine speed not dropping when releasing the throttle?
2 Answers
The reason for the engine speed not dropping when releasing the throttle is: the throttle spring has been in a compressed state for a long time, resulting in reduced tension, increased throttle opening, and increased fuel supply, causing the speed indicator to return slowly. It could also be due to faulty components or air leakage in the intake manifold. If the vehicle has just undergone maintenance, a slow drop in engine speed is not considered a fault. The engine speed affects the number of work cycles per unit time or the effective power output of the engine, meaning the engine's effective power varies with different speeds. For the same engine model, the rated power value may differ depending on its application, and the effective torque also changes with engine conditions. The maximum torque output and its corresponding speed are used as indicators to evaluate the engine's performance in automotive applications.
My old car had this issue before where the RPM would stay high after releasing the throttle and wouldn't drop, which was really annoying. The cause might be the throttle pedal itself not resetting, possibly due to a stuck or aged spring, making it feel rough when pressed. On the electronic side, if components like the throttle position sensor or idle control valve have too much carbon buildup or a short circuit, the ECU might misjudge and keep supplying fuel to maintain high RPM. Later, I found a vacuum leak during inspection—inaccurate air intake affected RPM control. Also, poor transmission matching can cause chaotic shift logic, which may keep RPM elevated. Don't delay fixing this, as it wastes fuel and accelerates component wear. I suggest first checking pedal rebound, then using an OBD scanner to read trouble codes, or directly sending it for repair to diagnose electronic and mechanical issues.
