Why Should the Engine Start-Stop Function Be Turned Off on Rainy Days?

[LeHarrison]

The reason to turn off the automatic start-stop function in cars on rainy days is to prevent water from being sucked into the engine when driving through deep puddles, which can cause the engine to stall. If the engine restarts automatically in such a situation, it is equivalent to a secondary start of the vehicle, and the water in the combustion chamber cannot be compressed. This can lead to severe damage or even complete failure of the engine, hence the caution is advised during rainy days. Below is an introduction to the automatic start-stop function: 1. Limitations: The use of the automatic start-stop function is subject to certain conditions. It may not function properly if the car's battery does not have sufficient charge, if the battery temperature is too high or too low, or if the seatbelt is not fastened while driving. 2. Principle: By equipping a traditional engine with an enhanced motor that has an idle start-stop function, the engine can be completely shut off when the conditions for idle stopping are met. When the vehicle needs to move again, the idle start-stop motor quickly responds to the driver's start command, rapidly restarting the engine to reduce fuel consumption and exhaust emissions.

[KadenRose]

Every time I drive in the rain, I manually turn off the auto start-stop function for a simple reason—the risk of water accumulation is too high. When the car automatically shuts off at a red light or while parked, and you press the accelerator to restart the engine, if the road has deep standing water, water can be sucked into the intake, leading to hydro-locked cylinders and seized pistons. It’s like flooding the engine internals, and repairs can cost at least a few thousand dollars. Water deeper than 10 cm is especially dangerous, particularly in heavy rain or flood-prone areas. Additionally, high humidity can cause electrical connectors to short-circuit, leading to starting system failures and compromising driving safety. I believe the fuel-saving benefit of this feature is minor compared to the major safety hazard. Keeping the engine running in rainy conditions is the safer choice, avoiding unnecessary repair headaches and ensuring more responsive braking.

[LaReid]

During heavy rainstorms, I always make it a habit to turn off the auto start-stop system first. While it's designed to be eco-friendly and fuel-efficient by shutting off the engine when idling, restarting in standing water risks sucking water into the engine's intake manifold. This can cause hydraulic lock (commonly called hydrostatic lock) inside the engine, which can completely destroy the powertrain. Damp conditions may also allow water ingress into wiring harness connectors, causing short circuits and triggering electronic control failures. Checking water depth is actually simple: if it reaches halfway up the tires, don't take the risk. There's another advantage to disabling this feature in rain – more reliable braking performance. The restart delay might make you react slower on slippery roads. Every time I adjust it, I feel significantly more at ease.

[ChristianRose]

Turn off the auto start-stop function when driving in the rain, and the reason is obvious: water entering the engine would be disastrous. If the car stops and then restarts, accumulated water can easily be sucked into the intake valves, leading to a hydro-lock incident, and the repair costs won't be cheap. High humidity can also cause electrical failures, potentially leading to system malfunctions. I never overlook this—turning off the button is simple and safe. Keeping the engine running ensures faster brake response, making driving in the rain much safer.