What are the reasons for the increase in engine speed?
2 Answers
The reasons for the increase in engine speed: 1. Throttle assembly failure: If the throttle fails, causing the throttle opening to suddenly increase, resulting in a sudden rise in vehicle speed; 2. Fuel pump and fuel system issues: Fuel injector leakage or blockage, leading to inability to inject fuel as instructed by the electronic control unit, causing the air-fuel mixture to be too rich or too lean, resulting in poor operation of individual cylinders and unstable idle speed; 3. Excessive carbon deposits; 4. Air conditioning clutch slipping or damage: Manual transmissions, dual-clutch transmissions, semi-automatic transmissions, and other forms of gearboxes use friction plate clutches to transmit engine power. If the clamping torque is insufficient or the friction plates are severely worn, slipping will occur, leading to high engine speed without a corresponding increase in vehicle speed.
I've been driving trucks for over a decade on long hauls, and engine RPM spikes are all too common. It's normal when you step on the gas to accelerate. But if it happens for no reason, you need to pay attention: it could be the throttle pedal sticking or being pressed down by the floor mat; an air leak in the system causing the engine to suck in extra air and rev up; a dirty throttle body sticking in position, prompting the ECU to inject more fuel; a high idle due to carbon buildup in the idle control valve; faulty signals from sensors like the crankshaft position sensor misleading the ECU; or transmission slippage, like a worn clutch, causing the RPM to rise under light load. Ignoring it can double fuel consumption and damage the engine. Regularly cleaning the air filter and idle control valve can prevent many issues. It's best to develop a habit of checking the throttle position before starting up—it ensures safety and saves fuel.
