What Causes a Car to Stall When Not Pressing the Accelerator?
2 Answers
Car stalling when not pressing the accelerator can be attributed to the following reasons: Fuel System Malfunction: During normal engine operation, the fuel pump draws fuel from the tank, which passes through the filter into the distribution line and is then sprayed by the injectors to form an air-fuel mixture. In this process, the fuel pump and injectors are the most prone to failure, followed by filter and fuel line blockages. If necessary, the fuel system can be cleaned. To minimize such occurrences, always refuel at reputable gas stations with the correct octane rating and ensure timely fuel replenishment, avoiding letting the fuel level drop below the red line. Throttle Body Blockage: The throttle body is undoubtedly the most critical component and also the most susceptible to issues. Typically, mechanics will consider cleaning the throttle body. However, if frequent cleaning does not fully resolve the stalling problem, it usually indicates a fault. Additionally, check the vacuum pump to ensure normal air intake. Abnormal Spark Plug Ignition: In a gasoline engine, the air-fuel mixture is ignited by the spark plug near the top of the compression stroke. Therefore, when the spark plug fails, it naturally leads to vehicle stalling. In such cases, replacing the spark plug is recommended. If replacement is inconvenient, temporary solutions like cleaning the electrodes or adjusting the central electrode length can be employed. Other factors like insufficient battery voltage, leakage, faulty ignition coils, or wiring issues can also cause poor ignition or stalling. Sensor Malfunction: Check whether various sensors and actuators are functioning properly. Key sensors include the throttle position sensor, oxygen sensor, and crankshaft position sensor. If the crankshaft position sensor has been replaced, also verify whether the oxygen sensor is contaminated.
I've encountered this situation before, and it's usually due to issues with the idle control system, such as a clogged idle control valve or faulty sensor. It could be caused by a dirty throttle body or an inaccurate mass airflow sensor, preventing the engine from maintaining normal RPM in neutral. Worn spark plugs or problematic ignition coils can also cause stalling, as the engine loses its support point when you're not pressing the accelerator. Additionally, the fuel system might be delivering insufficient fuel, possibly due to clogged injectors or low fuel pump pressure. Vehicles that haven't been regularly maintained are more prone to this issue. I recommend first checking if the air filter is dirty or clogged and cleaning the throttle body. Frequent stalling can be dangerous while driving, especially when losing power during turns, which could lead to collisions. For troubleshooting, try cleaning the throttle body yourself first. If that doesn't work, seek professional diagnosis at a repair shop without delay. Safety comes first.
