What Causes Engine Shaking at Idle Speed?
2 Answers
Regarding the specific reasons for engine shaking at idle speed: 1. Severe engine carbon buildup caused by a dirty throttle body or excessive carbon deposits in the fuel injectors. When there is too much carbon buildup inside the engine, the gasoline sprayed by the fuel injectors during cold starts is largely absorbed by the carbon deposits, resulting in an overly lean air-fuel mixture and difficulty starting. 2. Ignition system malfunction. Over time, components such as spark plugs, high-voltage wires, and ignition coils can degrade, leading to poor ignition system performance. 3. Unstable fuel pressure. This can be caused by abnormal fuel pump pressure or incorrect readings from the intake pressure sensor, which can cause the engine to shake. 4. Aging engine components. When electrical systems are turned on while the engine is idling, it increases the engine load, causing the idle speed to drop.
When I was waiting at a red light while driving, the engine suddenly started to shake, feeling as uncomfortable as sitting on a massage chair. Common causes include aging spark plugs with carbon buildup, which can lead to uneven ignition. Spark plugs tend to wear out after a few years and need timely replacement. Faulty ignition coils often cause misfires and shaking, disrupting the engine's smooth operation. A dirty or clogged throttle body can restrict airflow and requires regular cleaning. Additionally, clogged fuel injectors can result in uneven fuel supply. Ignoring these issues can increase fuel consumption, shorten engine lifespan, and even lead to dangerous stalling. I’ve tried inspecting these parts myself—if a problem is found, it’s best to fix it immediately before it worsens. Ideally, take the car to a trusted repair shop for a check-up. In any case, don’t ignore it; address the issue early to avoid damaging the car and wasting money.
