What are the symptoms of a faulty RPM sensor?
3 Answers
Engine sensor failure symptoms include: 1. Unstable engine idle; 2. Momentary stalling or engine shutdown when starting or decelerating to stop; 3. Reduced engine acceleration performance; 4. Deviation in the speed display on the instrument panel; 5. Illumination of the engine warning light. Sensors are typically installed on the distributor or engine, detecting crankshaft rotation angle. Failure disrupts the ignition system, preventing engine operation. Most RPM sensors are magnetic pulse type, generating weak electrical signals that can be tested using a multimeter or oscilloscope.
A faulty RPM sensor can make the car very difficult to start. Like last time when I drove my old car, it took forever to crank up – the engine seemed to be struggling. It gets worse while driving, with frequent stalling, especially when idling at red lights where it shakes violently like a disobedient child. On the highway, acceleration feels weak, speed won’t pick up, and fuel consumption spikes. The tachometer needle often jumps erratically or fluctuates, and sometimes the check engine light comes on, flashing annoyingly. This issue has significant consequences—incorrect signals confuse the ECU, potentially causing mistimed ignition, and prolonged neglect increases engine wear. I recommend getting it checked at the first sign of trouble. Replacing the sensor isn’t expensive, so don’t delay until major repairs are needed—safety comes first.
When the RPM sensor fails, the engine performance drops directly. With years of driving experience, I've encountered this issue several times: noticeable startup delay, often taking 2-3 seconds to ignite; unstable idling with sputtering sounds and white smoke from the exhaust pipe; lack of power during acceleration, with fuel consumption surging by over 10%. Fault codes often show P0335 or similar, and the dashboard tachometer fluctuates wildly or resets to zero. In severe cases, it affects automatic gear shifting, causing erratic gear changes or delayed upshifts. The sensor is responsible for position and RPM signals—if it fails, the entire electronic control system malfunctions. You can check it yourself using a multimeter to measure voltage, but most people take it to a repair shop. Preventive measures include regular maintenance, as these sensors typically last around 80,000 kilometers.
