What Causes the Engine RPM to Increase but the Vehicle Speed Not to Rise When Accelerating?
2 Answers
The reason why the engine RPM increases but the vehicle speed does not rise when accelerating depends on whether the engine is paired with a manual transmission or an automatic transmission. The fact that the RPM increases when the accelerator is pressed indicates that the engine's power operation is functioning properly. The inability to increase speed suggests that there is damage in the components transmitting power to the transmission. If a manual transmission is used, the common main causes are issues with the clutch or the transmission itself. The clutch acts as an intermediary for power transfer between the engine and the transmission. If the clutch friction plate is slipping, it can lead to a loss of power. Manual transmissions have high transmission efficiency. If the clutch is functioning correctly, possible faults could be related to the output shaft or the engagement gears of the selected gear. For automatic transmissions, a common main reason is the torque converter not locking up. Normally, when the engine RPM, vehicle speed, and throttle depth reach certain levels, the torque converter locks up. If it fails to lock up, it can result in the engine revving without the vehicle accelerating. This phenomenon is mainly observed in vehicles equipped with torque converters, such as all ATs and some CVTs. In this regard, dual-clutch transmissions perform much better. Solutions for high RPM without an increase in vehicle speed: First, check the level of the transmission hydraulic fluid. If the fluid level is too low or too high, it should be adjusted accordingly. Then, observe whether the transmission continues to slip. If slipping persists, inspect the quality of the hydraulic fluid. If the fluid appears dark brown or has a burnt smell, it indicates that the friction plates of the clutch or brake, or the brake bands, are burnt. In such cases, the transmission needs to be disassembled for repair. Additionally, a road test can be conducted to determine if the automatic transmission is faulty. Shift the gear lever into different positions and drive the vehicle. If the engine RPM suddenly increases when the automatic transmission shifts to a certain gear, but the vehicle speed does not rise accordingly, it indicates that the gear is slipping. The easier it is for the engine RPM to increase during slipping, the more severe the slipping is.
My car had a similar issue before, where stepping on the gas pedal caused the RPM to surge but the speed wouldn't increase. It's usually a problem with clutch slippage. With manual transmission cars, the clutch plates wear out over time, and when you press the accelerator, it feels like the engine is revving without any grip, and the car won't move. It could also be due to insufficient or degraded transmission fluid, affecting power transfer, or torque converter failure in automatic transmission cars. Once, this happened to me on the highway, and I quickly pulled over to check, only to find the clutch smoking—it was really scary. I recommend not forcing the car to drive in this condition, as it can damage more components. Take it directly to a repair shop to check the clutch plates and transmission fluid, and replace parts if necessary. In daily driving, try to minimize riding the clutch, and regular maintenance can extend its lifespan. Safety first.
