If your car shuts off when the brakes are pressed it’s likely due to the idle speed dropping too low when the transmission is in gear. Aside from that inconvenience, it’s a problem that can signal issues with your brake system.
I experienced this problem in a Camero with a carbureted engine. The car had an automatic transmission and when I stepped on the brake pedal, the RPMs would dip until the engine shut off. Fuel injected automobiles also experience this engine hiccup.
Let’s take a quick look at twelve reasons why your car shuts off when the brakes are pressed.
1. Issues with the Idle Control Valve
One major reason why your car shuts off when the brake is pressed is because of a failing idle control valve. An idle air control valve is responsible for monitoring the air intake as it’s mixed with fuel before its injected into the cylinders. In most cars, when the engine speed drops below 1000 RPM, the engine will shut off. Usually this indicates a dirty or faltering idle control valve.
2. Low Fuel Pressure
The correct amount of fuel pressure helps an engine run efficiently. But if fuel pressure is low or non-existent, it can cause your car to shut off when the brakes are pressed. Normal fuel pressure is based on a car’s fuel system and engine. The typical range for a modern fuel injected engine is 60 PSI. Low fuel pressure can be caused by a faulty fuel pump, bad fuel regulator, and/or malfunctioning injectors.
3. Bad Fuel Pump
A bad fuel pump can wreak havoc on a car’s performance. The fuel pump is part of the fuel system and one of the most replaced parts of that system. It’s responsible for sending gasoline from the gas tank to the engine. Fuel pump failure can be caused by wear and tear, contaminated fuel from dirt, moisture and bad gasoline or electrical issues. If it’s damaged in any way, it won’t have enough pressure to send fuel to the engine which can cause your car to shut off when the brakes are pressed.
4. Torque Converter Issues
In a car with a manual transmission, the engine connects to the transmission by a clutch. In a car with an automatic transmission, the engine connects to the transmission via a torque converter. Part of the job of a torque converter is to help a vehicle come to a complete stop without the engine dying. But if the torque converter clutch can’t disengage as you slow down, the result is an engine that will sputter to a stop.
5. Restricted EGR Valve
One of the most crucial elements of the exhaust system is the exchange gas recirculation (EGR) valve. It recycles a part of the exhaust gas from an engine back into the combustion chamber where it combines with fresh air from the intake to lower emissions. An EGR valve, however, can become stuck in its open position due to carbon build up which can cause the engine to stall and even shut off during braking.
6. Low Transmission Fluid
Transmission fluid helps keep an automatic or manual transmission lubricated and cool. It also serves as viscous fluid to help transmit power from the engine > to the transmission > to the drive wheels. Low transmission fluid can absolutely make an engine stall and even shut off. This is because there’s not enough fluid to lubricate the hydraulics or prevent overheating.
7. Bad Oxygen Sensor
Also called an O2 sensor, an oxygen sensor works with the fuel injection system to maintain performance. It measures how much unburned oxygen is in the exhaust. This information is sent to the ECU (electronic control unit) to help it figure out the right air to fuel mixture at any given moment. But since the O2 sensor is in the exhaust stream, it can become gunked up by oil or a rich air to fuel mixture resulting in incorrect readings which can cause your car to shut of when the brakes are pressed.
8. Dirty Fuel Injectors
Fuel injector maintenance is integral for optimal engine performance. They’re part of a car’s fuel delivery system. Fuel injectors also work with the ECU to deliver the right amount of fuel into the cylinders at the right time. Old fuel, carbon and residue inside the fuel can cause fuel injectors and/or their filter baskets to become clogged. When that happens, it can cause your car to shut off when you apply the brakes.
9. Vacuum Leak in Power Brake Booster
A brake booster amplifies a car’s braking ability when you put your foot on the brake pedal. Vacuum brake boosters use vacuum feed from the engine to boost the power of the brake. But if there’s a leak somewhere in the booster, it will take in more boost power than you need when you apply the brakes. This takes vacuum away from other components causing the engine to stall and shut off when you apply the brakes.