Updated at: 17-07-2022 - By: Lucas

When the brake pedal is depressed, the engine can stall for a variety of reasons. Additionally, this issue may be an indication of brake system issues that you should investigate. As a result, you should avoid driving the vehicle until the problem has been resolved.

Carburetor-powered vehicles were more likely to have engine stalling while braking, but injection engines may also be affected. In order to understand why an automobile stalls, we’ll go over the five most common causes. In order to find out what caused the problem, you will need to do a thorough inspection.

What are the causes of engine stalling when braking?

Car Stalls When Braking

  • A bad or failing vacuum brake booster;
  • Vacuum brake booster hose depressurization;
  • Malfunctions of the idle speed sensor;
  • Incorrect operation of the engine electronic control unit (ECU);
  • Bad or failing fuel pump.

A bad vacuum brake booster

Between the pedal and the primary brake cylinder, the vacuum booster is situated. Its function is to dissipate the force generated by the driver’s application of pressure to the brake pedal. A vacuum hose connects the vacuum brake booster to the intake manifold. A membrane is also part of the vacuum brake booster’s design. When braking, if this membrane is destroyed, the car will stall out.

Brake system air enters fuel mixture if the membrane is destroyed since it doesn’t have time to establish vacuum. When you push the brake pedal, the engine stalls.

We recommend that you replace the vacuum amplifier if it fails, even though it is possible to repair it.

How to check the vacuum brake booster?

Because of this, there are two simple methods to determine whether or not the vacuum brake booster hose is damaged.

This is a good starting point.

  • First, stop the engine;
  • Press and release the brake pedal several times. At first, the pedal stroke will be softer but after pressing several times, it will become harder.
  • Keep the pedal in the lower position;
  • Start the engine;
  • If after starting the engine, the brake pedal stroke becomes softer again, then there is no problem with the vacuum hose. But if it still remains still, then you need a detailed check.

a second strategy

  • After the engine has been running for some time, press the brake pedal and then stop the car
  • Keep the brake pedal pressed for about 20-30 seconds;
  • If during this time the pedal does not resist the foot, then everything is functioning properly with the vacuum brake booster.

Bad or worn vacuum brake booster hose

Car Stalls When Braking-3

Depressurization of an intake manifold-to-vacuum booster hose can also cause the car to stall while braking. Extra air will enter if this hose is damaged, resulting in an improper air-fuel combination, which will cause the engine to stall when the brake pedal is pressed hard.

Remove the vacuum booster’s hose to inspect the hose. Start the engine and insert your finger into the hole left by the removed hose. Adding a finger to a sealed engine raises RPMs; removing the finger from a sealed engine lowers them.

The engine will run at a constant pace if the pipe is allowing air to travel through.

The end of the hose that connects to the amplifier should also be checked for a valve. There must be no air leakage through the valve in order to avoid the aforesaid symptoms.

A vacuum cleaner that isn’t working properly can usually be diagnosed by simply touching it. You’ll have to exert more effort to squeeze the brake pedal if it’s leaking air.

Vacuum brake booster malfunctions can also pose a safety risk because it will need more effort from the driver to apply the brakes and will increase the stopping distance. As a result, the fastest possible resolution to this problem is preferred.

A bad fuel pump or fuel filter

Car’s Electronic Control Unit (ECU) will tell the engine to stop receiving fuel when the vehicle is braking. Loss of traction occurs when the engine’s fuel pump is unable to produce the needed level of power or is blocked with debris as a result of a malfunctioning fuel pump or fuel filter.

A pressure gauge can be used to check the fuel line pressure. There are certain pressure levels listed on each cylinder in your car’s owner’s manual.

However, if you have any suspicions that the fuel filter may be faulty, it is best to replace it and be on the safe side.

In rarer cases, defective high-voltage wires are to blame for a car’s inability to stop when you brake. If the battery’s negative contact wire is of low quality, the engine may stop if you suddenly apply the brakes. This should be checked as well.

A failing idle speed sensor

The idle speed sensor is responsible for starting and maintaining the engine’s speed at idle. As soon as this sensor fails, the engine will stall due to a loss of torque. When you press the accelerator, the engine RPM should rise.

The resistance of the sensor’s internal windings can be checked with a suitable multimeter tester. Connecting to different contacts is necessary depending on the design; consult the owner’s handbook to verify that the values listed there match yours.

A new sensor must be installed if the idle speed sensor malfunctions.

A failing Electronic Control Unit (ECU)

An authorized car shop with a computer diagnostic is the ideal place to look for ECU malfunctions, which might be difficult to identify, so it’s advisable to bring the car in for a checkup.

Engine with LPG stalls when braking

It’s possible that an inaccurately setup gearbox is in your automobile if it’s an older type LPG gas without its own ECU. In high-speed situations, when the brake pedal is rapidly depressed, the throttle is closed, and the incoming air drains the mixture.

Gas reducers have vacuum mechanisms that only release a limited amount of gas when the engine is idle, which is further depleted by incoming airflow.

This problem can be resolved by reprogramming the transmission to idle so that more gas is delivered to the engine.

Other justifications for LPG automobiles indicates that the electric valve’s filter has become blocked, causing the aforementioned issue. Regardless of whether or not your LPG system has one of these filters, you must clean or replace it to fix the problem. Otherwise, the poor mixture can be caused by the counter-flow of air.


When a car stalls when braking, it can be quite inconvenient. A common cause of this issue is the vacuum booster and the hose that connects to it. As a result, please verify theĀ 

following two sections. If everything checks out, I’d suggest taking your vehicle to a mechanic to get thoroughly inspected.