Why does the car stall and fail to start when hot?
2 Answers
Reasons why a hot car stalls and fails to start: 1. Carbon deposits: At high temperatures, carbon deposits have a strong adsorption effect on fuel. If there is excessive carbon buildup on the piston, throttle valve, and intake pipe, it can absorb some of the fuel, resulting in a lean air-fuel mixture and affecting engine startup. 2. Faulty coolant temperature sensor and intake air temperature sensor: If these two sensors are damaged, they cannot provide accurate temperature signals. 3. Fuel system failure: When the car is hot, the temperature is very high. If low-quality gasoline is used, it can cause the gasoline to evaporate, resulting in an overly lean mixture. Additionally, poor operation of the fuel pump or fuel injector leakage can also make it difficult to start the engine.
I've worked in an auto repair shop for twenty years, and I see issues like engine stalling when hot and failing to start every day. Eighty percent of the time, it's a problem with the crankshaft position sensor—this part tends to fail under high temperatures, causing the ECU to lose the RPM signal. It could also be a failing fuel pump, especially in older cars where the carbon brushes in the fuel pump motor wear out and stop working when the engine is hot. Not long ago, I fixed an old Volkswagen Bora where the fuel pump connector was burnt out. Also, don’t overlook a faulty coolant temperature sensor—it sends incorrect signals to the ECU, messing up the air-fuel mixture. I recommend going to a repair shop to read the trouble codes, focusing on these three components. Regularly changing the fuel filter can help extend the fuel pump's lifespan.