What Causes Unstable Idle Speed in New Cars?

[CarolineFitz]

New car idle instability is caused by: 1. Air, gasoline vapor, or combustion exhaust entering the intake manifold, resulting in an overly rich or lean air-fuel mixture; 2. Ignition module failure, incorrect spark plug gap, spark plug electrode erosion or damage, excessive high-voltage wire resistance; 3. Injector clogging, fuel filter blockage, fuel pump screen obstruction, fuel pressure regulator failure, return line blockage, and other faults leading to an overly rich or lean mixture; 4. Failure or damage of the engine intake system's actuators; 5. Excessive carbon buildup on the throttle body and surrounding intake passages, altering the air channel cross-sectional area, preventing the control unit from precisely managing idle air intake.