What causes slight shaking when the car is idling?

[LeAlexis]

The reasons for a car shaking during idle are as follows: 1. Intake system failure: Excessive carbon buildup in the throttle body and intake manifold, clogged air filter element, leaks in the intake pipe or EGR valve, faulty intake pressure sensor. 2. Fuel system failure: Fuel supply pressure issues, faulty fuel injectors. 3. Ignition system failure: Spark plugs not firing or weak spark energy, faulty ignition module or ignition coil, malfunctioning sensors or ignition control circuit. 4. Electronic control system failure: Internal circuit damage or poor contact in the electronic control system. 5. Mechanical structure failure: Damaged or weakened piston rings, carbon buildup in piston ring grooves, carbon deposits in cylinders, bent or deformed connecting rods, incorrect timing belt installation. 6. Other reasons: Air conditioning system, automatic transmission, etc., which increase engine idle load, clogged catalytic converter, imbalance in rotating components such as the crankshaft and flywheel.

[DylanLynn]

As a car owner, my car has shaken several times at idle, usually due to ignition system issues, such as aging spark plugs or a faulty ignition coil, which cause an imbalance in the engine's cylinder operation, leading to vibrations. Fuel system problems are also common, like excessive carbon buildup in the fuel injectors, uneven fuel supply, or unstable air-fuel mixture, which can also cause shaking. Additionally, worn or loose engine mounts can transmit vibrations into the cabin when parked, making it very noticeable. Excessive carbon buildup, especially in the throttle body and intake ports, affects idle stability and can increase fuel consumption in severe cases. Cold or hot starts may also worsen the shaking. I once fixed it myself by replacing the spark plugs and cleaning the fuel injectors, which only cost a few hundred bucks. If not addressed promptly, it not only affects driving comfort but may also damage the engine, so it's best to get it checked as soon as possible. Regular maintenance, like replacing filters and cleaning the fuel system, can prevent this issue from occurring.

[HarleyFitz]

This is a common issue. Idle shaking is mostly caused by poor ignition, such as excessive spark plug gap or carbon buildup leading to delayed ignition, resulting in unstable engine operation. Insufficient fuel pump pressure or clogged fuel injectors can also cause shaking due to uneven fuel supply or poor intake/exhaust flow. Air system problems, like a dirty throttle body or clogged air filter, can cause fluctuating air intake affecting idle. Loose engine mounts make it easier for vibrations to transfer to the body. Faulty idle control valves or sensor misreporting are also potential causes—for example, a faulty temperature sensor causing incorrect ECU adjustments. Severe carbon buildup often leads to shaking accompanied by increased fuel consumption. It's recommended to use a diagnostic tool to read fault codes first, avoiding unnecessary part replacements and saving money. Regularly taking long drives to burn off carbon and keeping the fuel system clean can help minimize such issues.

[SanJulia]

My car was shaking annoyingly at idle. When I asked at the shop, the mechanic said it might need new spark plugs or the fuel pump could be failing. After cleaning the fuel injectors and throttle body, it became much smoother immediately. Sometimes a bad engine mount can also cause severe shaking, which can be fixed for just a few hundred yuan. Avoid frequent short trips to reduce carbon buildup and develop good habits. Get simple checks or have someone fix it - safety comes first.