Why does the car shake and stall at idle speed?
4 Answers
Car shaking and stalling at idle speed is 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 cold-start fuel injector will be largely absorbed by the carbon deposits, resulting in an overly lean air-fuel mixture during cold starts and making it difficult to start the engine. In this situation, the car will only start easily once the carbon deposits have absorbed enough gasoline to reach saturation. An engine is a machine that converts other forms of energy into mechanical energy. It was invented in the UK and can refer to either a power generation device or the entire machine including the power unit (such as gasoline engines, aircraft engines). Types of engines include internal combustion engines (e.g., gasoline engines), external combustion engines (e.g., Stirling engines, steam engines), and electric motors.
I remember once when I was waiting at a red light, my car suddenly started shaking violently and almost stalled, which scared me so much that I immediately pulled over. Later, after inspection, it turned out that the throttle was too dirty, with excessive carbon buildup affecting the air intake, leading to unstable idling. Another common issue is the ignition system, such as worn-out spark plugs or faulty ignition coils, causing rough starts. Problems like clogged fuel lines or incorrect fuel injection from the injectors can also have an impact. Some cars experience this due to aging engine mounts, which reduce vibration damping, allowing the vibrations to be directly transmitted. If you encounter this situation, don’t panic—first check the air filter and throttle. If the shaking occurs right after maintenance, it might just be the computer adjusting to new data, and it should resolve itself in a couple of days. If the problem persists, it’s best to visit a repair shop early and have them read the fault codes with a diagnostic tool.
I've encountered the issue of car idle shaking and stalling many times. Based on my experience, there are several main causes: Engine carbon deposits are particularly important, especially for older vehicles that have traveled tens of thousands of kilometers. When the throttle body and fuel injectors are clogged with carbon deposits, insufficient air intake or inaccurate fuel injection can cause shaking. Then there's the ignition system - if spark plugs wear out and the gap becomes too large, or if ignition coils leak electricity, poor ignition will cause jerking. Insufficient fuel pump pressure can also lead to unstable fuel supply, making the car prone to stalling at idle. Another small but important detail is the charcoal canister solenoid valve - if it fails, gasoline vapors can escape randomly, causing incorrect air-fuel mixture ratios and resulting in shaking. Worn-out engine mounts with poor damping can make the car feel like a massage chair when sitting inside. I suggest starting with cleaning the throttle body, which only costs a few dozen yuan. If the shaking persists, then check other components.
Idle shaking and stalling are usually caused by issues with the air-fuel mixture. When the engine is idling, the RPM is low, making it particularly sensitive to the air-fuel ratio. Excessive carbon deposits can reduce air intake, causing the mixture to become too rich and resulting in shaking. Dirty fuel lines or unstable fuel pump supply can lead to abnormal combustion and stalling. On the ignition side, weak spark due to worn-out spark plugs or leaking high-voltage wires can cause misfires at low speeds. Additionally, a faulty oxygen sensor can send incorrect data to the ECU, leading to inaccurate fuel injection adjustments and potential issues. A clogged exhaust pipe reduces exhaust efficiency, making the engine work harder and shake. Using fuel system cleaners regularly can help, but severe cases may require removing and cleaning the fuel injectors. It's safer to have the electronic throttle body cleaned and matched by professionals rather than attempting it yourself.
