What Causes Engine Shaking When Starting an Automatic Car?

[MacAlexis]

Here are the reasons for engine shaking when starting an automatic car: 1. Throttle: A dirty throttle causes uneven airflow, leading to shaking. 2. Fuel system: Poor fuel flow results in inadequate fuel supply at low throttle, causing uneven cylinder operation and shaking. 3. Transmission: Abnormal transmission operation. 4. High-voltage wires: Broken or burnt high-voltage wires or spark plug failure can cause cylinders to misfire, leading to unstable engine operation and shaking. 5. Battery voltage: Whether the battery voltage is within the specified range. Below are additional details on related causes: 1. Cause: The most common reason for car shaking is a dirty throttle or excessive carbon buildup in the fuel injectors. 2. Engine carbon buildup: When there is excessive carbon buildup inside the engine, the gasoline sprayed by the cold-start injector is largely absorbed by the carbon deposits, resulting in an overly lean air-fuel mixture during cold starts and making it difficult to start.

[OKhloe]

I've been repairing cars for many years and have dealt with numerous cases of engine shaking during automatic transmission vehicle starts. The most common issue is problems with the ignition system, such as severely worn or aged spark plugs, or failing ignition coils causing uneven ignition, which leads to unstable cylinder operation. The fuel system is also a critical factor; clogged fuel injectors or overdue fuel filter replacements can result in irregular fuel injection, affecting combustion efficiency. In the air system, excessive carbon buildup in the throttle body or a dirty air filter can disrupt air intake, causing an imbalance in the air-fuel mixture. Transmission components like a deteriorating torque converter or worn clutch plates can also lead to uneven power delivery, resulting in shaking. Additionally, aged or loose engine mount rubber can amplify vibrations by losing its damping effect. My advice is to first check simple components like spark plugs and filters and try replacing them yourself. If that doesn't work, use a diagnostic tool to check for error codes and take the car to a professional repair shop promptly to prevent further engine damage. Regularly using high-quality gasoline and adhering to scheduled maintenance can effectively prevent such issues.

[DelEmersyn]

I've been driving for over ten years, and recently experienced severe shaking when starting the car, which was quite frustrating. After some research, I found that replacing the worn-out spark plugs solved the issue, and there was also a problem with the ignition coil. A friend mentioned that a dirty throttle body could cause this, and cleaning it made the car run much smoother. Clogged fuel injectors are also common, especially when using cheap gasoline for extended periods, leading to carbon buildup and blockages. On the transmission side, torque converter slippage or clutch wear can cause uneven power delivery. I think developing a habit of regular inspections is practical, such as checking spark plugs and filters every 10,000 kilometers, rather than waiting until the shaking starts. Safety-wise, this issue really shouldn't be ignored—shaking during startup could lead to sudden stalling, which is especially dangerous on highways. Addressing problems early saves money on major repairs and helps the car last longer.

[DylanFitz]

From an automotive enthusiast's perspective, automatic transmission shudder during startup is often caused by uncoordinated engine combustion processes. Aging spark plugs failing to ignite or degraded ignition coil performance can lead to cylinder misfires and uneven power output. Fuel system issues such as carbon-clogged injectors affecting atomization, or uneven fuel injection disrupting the air-fuel mixture ratio. Air system problems like dirty throttle bodies or clogged air filters reducing intake volume interfere with proper combustion. Transmission components including poor lubrication inside the torque converter or worn clutches make power delivery unstable. Aged engine mounts losing elasticity fail to absorb vibrations, and severe carbon buildup can also disrupt compression ratios. Regular cleaning and replacement of critical components are key preventive measures to ensure smooth engine operation and safe driving.