What Causes Unstable Idle Speed in a Car Engine?
1 Answers
The reasons for unstable idle speed in a car engine: 1. When unwanted air, gasoline vapor, or exhaust gases enter the intake manifold, causing the air-fuel mixture to become too rich or too lean, leading to unstable idle speed; 2. Excessive carbon buildup on the throttle body and surrounding intake passages changes the cross-sectional area of the air passage, preventing the control unit from precisely controlling the idle air intake, which can also cause the mixture to be too rich or too lean, resulting in unstable idle speed; 3. The engine's intake system has many components, such as the throttle motor, idle speed control motor, duty cycle solenoid valve, air flow meter, and intake pressure sensor. Faults or damage to these components can cause unstable idle speed; 4. Clogged fuel injectors, clogged fuel filters, clogged fuel pump screens, faulty fuel pressure regulators, or clogged return fuel lines can all lead to incorrect fuel injection, causing the mixture to be too rich or too lean and resulting in unstable idle speed; 5. Faulty ignition modules, incorrect spark plug gaps, eroded or damaged spark plug electrodes, or excessive resistance in high-voltage wires can reduce ignition spark energy or cause misfires, leading to fluctuating and unstable idle speed.
