Car stalling when brake is applied causes
REASONS WHY CAR SHUTS DOWN WHILE SLOWING DOWN
Are you in dilemma of what is wrong with your car because your car works well when you are at high or steady speeds but as soon as you attempt to approach a stop, the engine switches off.
LISTED BELOW ARE CAUSES OF THE CAR SHUT DOWN DURING BRAKING:
1. Dirty/faulty throttle body
A throttle valve that is sticking or has broken gears can cause this car to go off while approaching a stop. Carb cleaner can be used to remove dirts or carbon from the throttle body. If the throttle body is faulty, it should be replaced.
2. Faulty idle stabilization valve or wrong idle adjustment setting
Idle speed that is not set correctly can make a car to go off while slowing down. This occurs when the idle speed is too low. For cars that have manual idle adjustment screw, this can be adjusted to correct idle engine speed. Some car's idle is automatically adjusted by the ECU.
3. Dirty/Faulty mass airflow sensor
A dirty or faulty Mass Air Flow sensor can send wrong signals to the ECU which will take decisions based on those wrong signals.
In some cases, it will send no signal at all. It can be cleaned with Mass Air Flow sensor cleaner. A faulty MAF sensor should be replaced.
4. Dirty/Blocked air filter
A very dirty or blocked engine intake air filter can starve the engine of air, especially at low engine speeds. This air starvation will cause the engine to go off as it requires both air and fuel to run. It will also limit power as it won't let enough air reach the engine at high engine revolutions.
5. Wrong engine timing
When there is no proper correlation between the crankshaft and camshaft, the engine might be going off at times. The crankshaft and camshafts are connected via timing belt or timing chain. Each engine has its timing procedure which should be strictly followed to correctly set the timing.
6. Faulty Crankshaft position sensor
A faulty crankshaft position sensor can make a car to shut down while approaching a stop. At times, this happens when the sensor has aged and has developed more resistance, even though its signal can still be seen on the diagnostic tool. When this is the cause of engine shut down, the sensor should be replaced.
Unfortunately, sometimes, it does show any fault code when it causes this fault.
7. Other sensors
Sensors like Oxygen/AF sensors, camshaft position sensor can cause engine shut down too when they send wrong signal or no signal at all.
8. Large vacuum leak
The effect of vacuum leaks are minimal at higher engine revolutions especially when the leak is not large. A large leak can cause engine shut down. Vacuum leak is the introduction of unmetered air into the engine.
9. Faulty transmission lockup system
As the vehicle speed reduces, the lockup clutch is supposed to disengage. If there is any problem that makes it not to disengage being it the electrical circuit that controls the lockup clutch or the mechanical system of the lockup clutch, it can make the engine to stall as it approaches a stop.
It is a good troubleshooting practice to use computerized diagnostic tool to get a good lead and to begin fault isolation from the simplest fault to the complex ones. For instance, it is not expected to begin timing adjustment before checking air filter or Mass Airflow meter.