What is the problem with engine idle shaking?
3 Answers
Idle engine shaking may be caused by issues such as engine intake pipe leakage, fuel system blockage or malfunction, spark plug problems, excessive engine carbon buildup, or aging. The following are the reasons for engine shaking: 1. Engine intake pipe leakage. The intake system has many intake manifolds or various valves, and any leakage will allow unwanted gases to enter, causing the concentration of the mixed gas in the intake manifold to be too high or too low, ultimately leading to intermittent shaking or weak idle symptoms in the engine. 2. Fuel system blockage or malfunction. Due to blockage of the fuel tank cap vent hole, fuel tank switch, fuel filter, or the fuel pipe between the fuel tank and the carburetor, the car cannot receive the corresponding amount of fuel during idle, causing the mixed gas to become lean, weakening the engine power output, and resulting in idle shaking. 3. Spark plug problems. If the spark plugs in the car's ignition system malfunction, it can cause poor ignition system performance, bad spark plug firing conditions, and other issues, leading to unstable operation such as shaking during idle. 4. Excessive engine carbon buildup or aging. Excessive carbon buildup inside the engine will cause the gasoline sprayed by the cold start injector to be largely absorbed by the carbon deposits, resulting in a lean mixed gas during cold starts and making it difficult to start.
I've been driving for twenty years and have encountered idle shaking issues several times. I remember once during a traffic jam, the car shook like an earthquake. After checking, it turned out the spark plugs were old, having been used for five or six years without replacement, causing unstable ignition due to large electrode gaps. Carbon buildup clogging the fuel injectors also disrupted the air-fuel ratio, making the engine struggle to breathe. Even worse, the engine mounts were broken, losing their shock absorption function and making the whole car shake more. It's recommended to replace spark plugs every 20,000 kilometers, use fuel additives to clean the fuel system, and address minor issues early. Prolonged engine shaking can damage cylinders and transmissions, affecting safety, so spending a bit on maintenance is worth it. If the shaking is severe, go to a reliable repair shop immediately for inspection.
As someone who tinkers with engines every day, idle shaking is often caused by ignition system failures. For example, worn spark plugs or faulty ignition coils can lead to a misfiring cylinder, causing engine imbalance. Unstable fuel pressure is another factor, where clogged fuel injectors or fuel pump issues result in insufficient fuel supply. Air intake leaks or broken vacuum tubes can make the air-fuel mixture too lean, worsening the shaking. Don't overlook engine mounts—older cars are prone to cracks that transmit vibrations. For quick diagnosis, plug in an OBD tool to read fault codes and address issues early. Delaying repairs can increase wear, spike fuel consumption, and raise driving risks. For peace of mind, have a professional technician check it out.
