What Causes an Automatic Transmission to Shake and Stall at Idle?
3 Answers
Automatic transmission shaking and stalling at idle can be caused by: 1. Electrical circuit faults, leading to stalling due to low-voltage power interruption while driving; 2. Component failures, typically involving the ignition coil, capacitor, or electronic ignition module; 3. Fuel system issues, such as a damaged fuel pump, ruptured fuel line, clogged carburetor fuel inlet, or an empty fuel tank. Solutions include: 1. Cleaning the fuel system and checking the idle control valve for carbon buildup, cleaning if necessary; 2. If spark plugs are excessively carbon-fouled, remove and clean them; 3. For idle shaking caused by unstable fuel pressure, first identify and repair leaks in the fuel delivery system, then test the injector's atomization performance, replacing components as needed.
Last time I encountered the issue of automatic transmission idling shaking and stalling, it took me a long time to figure out that it was caused by engine carbon deposits. After driving an old car for a long time, carbon deposits accumulate in the intake tract and cylinders, affecting the air-fuel mixture, which leads to incomplete combustion during idling, causing shaking or even stalling. Additionally, worn spark plugs or aging ignition coils are common culprits. They are responsible for ignition, and once their performance declines, the engine operation becomes unstable, especially when idling at a red light, where shaking becomes very noticeable. A dirty throttle body can also restrict air intake, and sensors like the mass airflow sensor, if dirty or faulty, can send incorrect signals to the computer, leading to erratic idle control. Issues in the fuel system, such as clogged fuel injectors or a dirty fuel filter, causing insufficient fuel supply, can also make the car shake. It's best to clean the throttle body, check the spark plugs, and replace the air filter promptly—these can be done DIY, but severe cases may require a visit to the repair shop. Regularly adding fuel system cleaner to remove carbon deposits can also help, preventing sudden stalling and breakdowns on the road.
I've been driving automatic transmission cars for over a decade and have encountered issues with idle shaking and stalling, which can be quite frustrating. Usually, it's caused by excessive carbon buildup, leading to poor engine performance. Spark plug problems are another culprit – I've had to replace them twice; when they wear out, the ignition becomes unreliable, causing the car to shake. Fuel system blockages are also a major cause, such as carbon deposits in the fuel injectors or low fuel pump pressure, disrupting fuel supply and making the car prone to stalling at idle. Additionally, unstable voltage from the car battery or alternator can affect the ignition system if the voltage drops too low. Faulty sensors like the mass airflow sensor or oxygen sensor can confuse the engine control unit, causing it to improperly adjust the idle speed and resulting in shaking. Regular maintenance is key to avoiding these issues: clean the throttle body and inspect the spark plugs every 10,000 kilometers. Air filters should be replaced periodically to ensure clean air intake, as dirty air can make it harder for the engine to run smoothly. If you notice problems, first check if the engine warning light is on, then take the car to a repair shop to read the trouble codes to prevent minor issues from turning into major ones.
