What Causes BMW Engine to Shake When Idling with AC On?
1 Answers
BMW engine shaking when the AC is on can be attributed to the following reasons: 1. Excessive carbon buildup in the throttle body and intake manifold: This alters the air passage cross-sectional area, preventing the control unit from precisely regulating idle air intake. This results in either overly rich or lean air-fuel mixture, causing incomplete combustion and subsequent vibration. 2. Faulty spark plugs: Weak sparks from individual malfunctioning spark plugs can compromise engine performance, leading to "misfire" symptoms and unstable idling. 3. Fuel pressure issues: Insufficient fuel pressure leads to poor fuel atomization from injectors, with fuel spraying in streams or even dripping in severe cases. Reduced fuel injection causes excessively lean mixture.