What Causes the Engine to Shake Every Few Seconds at Idle?
2 Answers
The most common reason for an engine shaking every few seconds at idle is a misfiring cylinder. Here are the relevant details: 1. Causes of Misfiring: There are many factors that can lead to a misfiring cylinder. For example, issues with the ignition system—check the condition of the spark plugs, high-voltage wires, and ignition coils. Poor performance of the ignition system or weak spark plug firing can also cause this type of problem. Solution: Check if the spark plugs are excessively carbon-fouled and replace them if necessary. 2. Severe Engine Carbon Buildup: The most frequent cause of car shaking is 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 cold-start injector can be largely absorbed by the carbon deposits, resulting in an overly lean air-fuel mixture during cold starts and making the engine difficult to start.
I've driven quite a few cars, and it's quite common to encounter a slight shake every few seconds at idle. The issue is mostly in the ignition system, such as old spark plugs or cracked ignition coils, where delayed ignition causes the engine to jerk. On the fuel side, carbon buildup clogging the fuel injectors leads to uneven fuel supply, and unstable injection each time will make the engine shake. A throttle body with too much carbon buildup does the same, as air can't get in, making it more noticeable at idle. The idle speed motor controls the RPM, and if it's stuck or faulty, it can also cause periodic trembling. Then there's the EGR valve in the emissions system—if the valve sticks, it disrupts airflow. I recommend not delaying; take it to a repair shop to check and replace the spark plugs and clean related components early. Regular maintenance is key—inspect the ignition and intake systems every 10,000 to 20,000 kilometers to prevent small issues from becoming disasters. Engine health directly affects driving safety, and higher fuel consumption isn't worth it either.
