What Causes Unstable and Fluctuating Car Idle Speed?

1 Answers
ReedLynn
07/30/25 2:08am
Car idle speed being unstable and fluctuating is caused by: 1. Severe engine carbon buildup; 2. Dirty throttle body or carbon deposits on fuel injectors; 3. Faulty spark plugs, high-voltage wires, or ignition coils leading to poor ignition system performance; 4. Unstable oil pressure, insufficient fuel pump supply pressure, or incorrect readings from the intake pressure sensor; 5. Fuel line blockage causing inadequate fuel supply; 6. Aging engine components. Solutions for unstable and fluctuating car idle speed: 1. Clean engine and idle speed motor carbon deposits; 2. Clean fuel lines; 3. Replace spark plugs, high-voltage wires, and ignition coils; 4. Clean air filter and throttle body; 5. Replace aging engine components.
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