Why does the engine speed rise abnormally when the accelerator is pressed?

[Justin]

Because a dirty throttle position sensor or voltage imbalance can cause electronic throttle failure, resulting in the situation where the speed does not increase even when the accelerator is fully pressed. Below is a related introduction about throttle speed: 1. Cause: The reason is that the torque converter is not locked. The throttle controls the opening of the throttle valve, affecting the engine's air intake. After pressing the accelerator, the amount of fresh air entering increases, and the fuel injection amount controlled by the ECU also increases, thus the force generated by combustion increases, pushing the engine's operating speed to rise. 2. Principle: Pushing the engine's operating speed to increase. Under normal circumstances, when the engine speed, vehicle speed, and throttle depth reach a certain level, the torque converter will lock. Before it locks, it is easy to encounter the situation where pressing the accelerator results in the engine roaring but the car not moving.

[DiGabrielle]

Last week, I encountered a similar situation while driving. When I pressed the accelerator hard, the tachometer shot up, but the speed didn't increase. My first thought was whether carbon deposits had clogged the throttle body, especially since it hadn't been cleaned in three years. Later, I realized it was more likely due to a dirty air filter affecting air intake or insufficient fuel pump pressure causing poor fuel delivery. Additionally, slipping clutch plates in the transmission can cause the RPM to rise without corresponding speed, particularly in manual transmission cars that are often driven in a semi-clutch state. Of course, sensor malfunctions are also common—for example, a drifting oxygen sensor can cause the ECU to mismanage fuel injection. Addressing these issues individually isn't too expensive, but neglecting repairs could eventually lead to costly transmission replacement.

[KinsleyRose]

As a seasoned driver who frequently navigates mountain roads, I've encountered several situations with abnormal RPM surges: the most frustrating is fuel system issues, where tank contaminants clog the fuel filter, causing intermittent fuel supply like asthma; turbocharged cars are more prone to wastegate valve sticking, where trapped exhaust gases make the turbo spin wildly; older vehicles require special attention to aging ignition coils, as unstable spark plug firing can trick the ECU into injecting extra fuel; modern cars' electronic throttle bodies are more delicate, where even a 0.1mm error in the pedal position sensor can cause erratic RPM fluctuations. Once my transmission fluid overheated, and the tachometer needle jumped around like a stopwatch. For these issues, I recommend reading trouble codes first—it's more reliable than blindly replacing parts.

[VonJohn]

High RPM without actual power delivery indicates a failure in the power transmission system. When the engine roars but the car doesn't move, it's likely clutch slippage—especially common in manual transmissions. Try starting in third gear with the handbrake engaged; if the car doesn't stall, that confirms it. For automatic transmissions, focus on checking the torque converter lock-up clutch—when faulty, it's like revving in neutral. Note that false TPMS alerts won't affect RPM, but a faulty wheel speed sensor disrupts transmission shift logic. My neighbor's SUV once hit 5000 RPM at 40 mph due to a failed driveshaft sensor.