What causes a car to fail to shut off?

[KaydenFitz]

Here are the reasons why a car may fail to shut off: 1. Automatic transmission models: Vehicles with automatic transmission rarely experience stalling, whereas manual transmission models may stall frequently due to insufficient driving skills. However, it's not impossible for automatic transmission cars to stall; the primary cause is the use of low-quality fuel (many gas stations sell impure fuel for excessive profits), leading to engine carbon buildup and stalling. 2. Reason two: For new cars (automatic transmission), stalling is mainly caused by insufficient driving proficiency. Another possibility is issues with the car's engine or fuel system, but for new cars, engine-related problems are less likely, with most cases being fuel system issues. 3. Reason three: Finally, for older models, aside from insufficient driving skills, stalling can be caused by using substandard fuel, which leads to engine carbon buildup and other related issues.

[VanAlejandro]

I've been repairing cars for 20 years and have seen many strange cases where the engine won't shut off. The most common issue is the ignition switch contacts getting welded together due to overheating. Even after turning the key, the engine keeps sputtering. In such cases, don't force the key out. First, shift to neutral, engage the handbrake, and then disconnect the negative terminal of the battery to cut power. If that doesn't work, it might be the body control module freezing up—you'll need to disconnect the power and wait five minutes for a reboot. With older German cars, be cautious of the starter relay sticking; the anti-theft warning light on the dashboard will flash. Once, a Honda owner had installed a GPS tracker that short-circuited—the dashboard stayed lit even after removing the key. We finally located and cut the aftermarket wiring in the fuse box to shut it down. Never force a solution in these situations; frying the control unit could cost you tens of thousands.

[ReidLee]

As a female car owner, I've encountered difficulty in turning off the engine twice. The first time was when I was driving my bestie's old BMW. After turning the key back, the engine kept shaking, which scared me so much that I immediately stepped on the brake, shifted to P gear, and restarted three times before it finally stopped. The mechanic said it was due to a malfunctioning signal from the transmission gear position switch, and a clunking sound when shifting gears should be a warning sign. The second time was with my family's new car, which would automatically start when the smart key was nearby. Later, I found out it was because the key had been dropped, causing signal confusion. Now I've learned my lesson: if the engine won't turn off, first press the brake hard and shift to N gear, then look for the red-lit fuse box in the engine compartment and pull out the 15-amp fuse labeled IGN. It's much more convenient than disconnecting the battery cables.

[LeJeffrey]

Those who have modified racing cars know that failure to shut off the engine is often due to stubborn electrical issues. My modified Civic once kept revving even after removing the key—it turned out to be a loose ground wire on the aftermarket ECU. For regular car owners, focus on three key areas in the ignition wiring: check if the terminals behind the ignition switch are melted, see if the ignition relay under the steering wheel is stuck (a hot outer casing indicates failure), and verify whether a substandard diagnostic tool is plugged into the OBD port. In emergencies, don’t remove the key to avoid steering wheel lock—instead, press the brake pedal hard with your left foot, shift to neutral, pull the hood release with your right hand, and rush to disconnect the ignition coil plug for safety.