Why does a car engine idle speed fluctuate?
1 Answers
Reasons for fluctuating idle speed in a car engine: 1. Oil accumulation and carbon deposits in the throttle body. A dirty or clogged intake tract can cause idle fluctuations, and carbon deposits or oil in the throttle body are common causes of unstable idle; 2. Weak spark due to faulty spark plugs; 3. Fuel system blockages, represented by clogged fuel injectors, and intake manifold issues; 4. Faulty sensors that prevent the ECU from controlling the correct air-fuel ratio; 5. Excessive or insufficient ignition timing. Fluctuating idle speed in a car engine is often related to signal sensor issues, such as the air flow sensor, Hall sensor, knock sensor, coolant temperature sensor, etc., and requires analysis with diagnostic tools.