Why does the engine speed rise rapidly after depressing the clutch pedal?
4 Answers
Here are the reasons why the engine speed rises rapidly after depressing the clutch pedal: 1. When the clutch is depressed and the power is disconnected, the engine loses load, which naturally causes the speed to rise momentarily. It's similar to how a person pedaling a bicycle would pedal in vain if the chain were to break. 2. In fuel-injected engines, the ECU automatically adds fuel when the gear is disengaged. In the past, truck drivers had to follow the sequence of 'depress-disengage-rev-depress-engage' when shifting gears. 'Depress' refers to depressing the clutch, 'rev' means adding fuel, and 'disengage-engage' refers to shifting up or down. Additional information about the clutch is as follows: 1. The clutch is located inside the flywheel housing between the engine and the transmission. The clutch assembly is fixed to the rear plane of the flywheel with screws, and the output shaft of the clutch is the input shaft of the transmission. 2. The clutch is a common component in mechanical transmissions, allowing the transmission system to be separated or engaged at any time. Its basic requirements include: smooth engagement, quick and thorough disengagement; easy adjustment and repair; compact size, lightweight, good wear resistance, sufficient heat dissipation capacity, and easy and effortless operation.
I remember when I was learning to drive, the instructor told me to press the clutch to shift gears, and the engine RPM suddenly shot up, which gave me a scare. Later, I figured out that pressing the clutch disconnects the engine from the transmission, as if the engine suddenly lost its load. The car's computer system detects the reduced load and automatically increases the throttle to raise the RPM, preventing the car from stalling. This is quite normal, especially common during gear shifts. If the RPM spikes too drastically, it's necessary to check for carbon buildup in the throttle or potential sensor issues. When driving normally, pay attention to gently pressing the throttle and avoid slamming the clutch at high speeds, so the RPM rise won't be too noticeable.
Having driven for over a decade, I often encounter the phenomenon of RPM surging when depressing the clutch. Simply put, when you press the clutch pedal, the engine's power is no longer transmitted to the wheels. The engine suddenly becomes idle without load, just like a kite losing wind. The car's computer detects this change and automatically increases fuel supply to raise RPM and prevent stalling. This situation occurs almost every time during gear shifts, which is completely normal. If the RPM rises abnormally high, such as suddenly jumping above 4000 RPM, it might indicate a faulty mass airflow sensor or a dirty idle control valve, requiring repair. During normal driving, try to shift gears smoothly and avoid abruptly depressing the clutch at high speeds.
From a technical perspective, the reason for the RPM rise when depressing the clutch is quite straightforward. I've thought about it - when the clutch disengages, the power transmission is interrupted, and the engine load disappears. The vehicle's control system then has to work to maintain the RPM. The computer increases fuel supply to ensure the engine doesn't stall. This phenomenon is common in manual transmission vehicles; it's reasonable for the RPM to briefly rise during gear shifts. If the RPM consistently stays high, it might indicate an issue with the throttle position sensor, which can be checked and fixed.
