What Causes Unstable Idling and Shaking in the Engine?
2 Answers
The causes of unstable idling and shaking in the engine are: 1. Aging of rubber components inside the engine mounts and transmission mounts; 2. Improper air-fuel mixture ratio in the engine compartment; 3. Carbon buildup on the valves and intake ports inside the engine, which absorbs a portion of the sprayed fuel-air mixture, reducing engine power and causing vibrations; 4. Malfunction of the coolant temperature sensor; 5. Improper air-fuel mixture ratio in the engine compartment. An engine is a machine that converts other forms of energy into mechanical energy, including internal combustion engines, external combustion engines, jet engines, and electric motors.
My old car was shaking like an earthquake at idle last month, with the RPM fluctuating up and down, so I started troubleshooting it myself. The ignition system was likely the issue, such as excessive carbon buildup on the spark plugs or aging ignition coils. When I took them apart, sure enough, the spark plugs were all black with carbon deposits. After replacing them with new ones, it improved significantly. Clogged fuel injectors can also cause uneven fuel supply—I checked and cleaning agents didn’t help, so I might need to replace the parts. Additionally, a dirty throttle body can restrict airflow, but spraying it with cleaner improved the situation a bit. I’ve been learning DIY car repairs for a while, and this kind of shaking is common in older models. Using fuel additives regularly can prevent carbon buildup. Don’t ignore it—delaying repairs could lead to increased fuel consumption or even engine damage. I’ve saved quite a bit on repair costs by doing it myself.
