What Causes Abnormal Engine Speed Signal?
2 Answers
Abnormal engine speed signal can be caused by the following reasons: Dirty Idle Speed Control Valve: This phenomenon is relatively common in electronic fuel injection vehicles, usually caused by a dirty (or damaged) idle speed control valve. When this occurs, it is recommended to clean the engine's idle speed control valve and carefully check whether the throttle valve is functioning properly or if there is any sticking due to excessive dirt. Incorrect Temperature Sensor Signal: An incorrect coolant temperature sensor signal can lead to an increase in idle speed. Due to intermittent faults in the coolant temperature sensor, it may transmit a coolant temperature far below the actual temperature, causing the control unit to mistakenly believe the engine is operating at a low temperature. This results in excessive air intake and fuel injection, leading to an abnormal increase in idle speed, which can exceed 2000r/min.
I'm the type who enjoys studying automotive mechanics. The most common cause of abnormal RPM signals is a faulty crankshaft position sensor. This component is installed near the engine and is responsible for monitoring the rotational position of the crankshaft. If it accumulates dust, gets damp, or suffers from aging internal components, the signal can drift and become inaccurate. Another common issue is wiring faults, such as loose connectors, worn insulation causing short circuits, or corroded plugs leading to transmission interruptions. The ECU control system may also malfunction due to programming errors or voltage instability interfering with signal processing. I've seen cars where these issues were ignored, resulting in sudden engine shaking, poor acceleration, or even stalling and breakdowns. When repairing, it's advisable to prioritize checking the sensor—cleaning or replacing it is cost-effective and can prevent major overhauls.
