How Long Will the Engine Stay On Without the Key in the Car?

[McWillow]

If the car key is taken out of the car, the engine will not shut off automatically. The car will only display a warning indicating that the key is not detected. For vehicles with push-button start, the key only transmits a signal to the ECU during the starting process. Once the engine is running, the fuel pump supplies fuel, and the engine will continue to operate as long as it is not manually turned off. However, leaving the engine running for an extended period, such as an entire day, can cause significant harm to the vehicle. The main risks include the following two scenarios: First, the engine remains in a low-speed operating condition, which makes the pistons and valves more prone to carbon buildup. This can lead to unstable idling and other adverse effects on engine performance, and may even shorten the engine's lifespan. Second, most vehicles are equipped with a three-way catalytic converter in the exhaust system, which is the most important external purification device for vehicle emissions. It converts harmful gases like CO from exhaust emissions into harmless substances such as carbon dioxide, water, and nitrogen through oxidation and reduction reactions. Prolonged idling with the air conditioning on makes it difficult for the catalytic converter to reach its optimal operating temperature, reducing its ability to process exhaust gases and negatively impacting its longevity.