car stalls when braking
Content
With a problem when car stalls when braking both the driver of a carburetor and an injection car can collide. Such a breakdown, in addition to inconvenience, can also lead to an emergency. After all, the car can stall not only during heavy braking, but also on a turn or in front of an obstacle. Most often, it is the drivers of cars with a carburetor that face such a problem. However, modern injection cars are not immune from such a nuisance. Reasons why an internal combustion engine may stall when pressing the brake pedal there may be several - breakdowns in the operation of the vacuum brake booster, depressurization of its hose, problems with the fuel pump or idle speed sensor (for injection). In this material we will provide you with the necessary information, which will help you fix the breakdown yourself. But you can reveal the true cause of the breakdown only after conducting an inspection and detailed diagnostics of the car.
Often, such a breakdown indicates a breakdown in the brake system, so we do not recommend using your car until the moment when it is fixed. This will protect you from creating accidents on the roads.
Main reasons
If the internal combustion engine of your car stalls when braking, then there can actually be a lot of reasons for this. However, the main ones are:
- breakdowns in the operation of the vacuum brake booster;
- depressurization of the VUT hose;
- problems in the operation of the gas pump;
- malfunctions in the idle speed sensor (for injection engines);
- incorrect operation of the vehicle's electronic control unit (if installed).
there are also a number of other, less common reasons, which we will also discuss below. So let's start in order.
Depressurization of VUT or its hose
The vacuum brake booster (abbreviated as VUT) serves to alleviate the effort that the driver creates by pressing the brake pedal. It is located between the master brake cylinder and said pedal. His work is connected with the intake manifold, to which he is connected by a vacuum hose. We will review his work later. The VUT design, in addition to other elements, also includes a membrane. If it is damaged or does not work correctly, this may be one of the reasons why it stalls when braking.
namely, when you sharply press the brake pedal, the faulty membrane does not physically have time to create a vacuum, which is why part of the air in the brake system enters the fuel mixture. This is the reason why the engine stalls when braking.
Such a breakdown can be easily identified on your own. The following algorithm of actions should be followed:
- turn off the car's internal combustion engine (if it worked before);
- several times (4 ... 5) press and release the brake pedal (at first the pedal stroke will be “soft”, and then the stroke will become “hard”);
- keep the pedal in the lower position with your foot;
- start the internal combustion engine;
- if at the time of starting the internal combustion engine the pedal “failed”, then everything is in order with the “vacuum tank” and the whole system, if it remains in place, you need to look for problems.
Checking the work of VUT
also one method:
- after the internal combustion engine has worked for some time, press the brake pedal;
- jamming the internal combustion engine;
- keep the pedal depressed for about 30 seconds;
- if during this time the pedal does not try to rise up and does not resist the leg, then everything is in order with the VUT and the entire system.
usually, the vacuum booster is not repaired, but change entirely, only in rare cases is repair possible, but not every master will undertake it. And not for any car such repair is expedient. Therefore, in the event of a VUT failure, we still recommend that you replace it.
also one reason why the car stalls when braking may be hose depressurization, which connects the vacuum brake booster and the intake manifold. The latter ensures the correct formation of the air-fuel mixture, which is fed further into the internal combustion engine. If the hose begins to let atmospheric air through, the mixture becomes very lean, due to which the internal combustion engine loses speed and even stalls if the brake pedal is pressed sharply.
You can check the integrity of the hose yourself using a visual inspection. you can also disconnect it from the vacuum booster. then start the engine and clamp the hole of the removed hose with your finger. If it is tight, then the internal combustion engine will automatically increase the speed, and after removing the finger, it will lower them again. In the event that the hose passes atmospheric air, the internal combustion engine will operate at constant speed during the above operations.
VUT check
At the end of the hose that connects it to the amplifier, vacuum valve installed. In the process of checking the hose, it is imperative to check its operation, so that it does not let air through. Otherwise, the consequences will be similar to those described above. That is, all work comes down to finding air leaks and the causes of system depressurization.
also one method of diagnosing a breakdown of the VUT is to “listen” for possible air leaks. It can exit towards the passenger compartment, from the brake pedal stem or towards the engine compartment. In the first case, the procedure can be carried out independently, in the second - with the help of an assistant. One person presses the pedal, the second listens to the hissing from the VUT or its hose. The easiest way to identify a breakdown of the vacuum cleaner is by tactile sensations. If it lets air through, then the brake pedal will work very hard, and in order to press it, you need to make a lot of effort.
The reason is the gas pump and fuel filter
also sometimes there is a problem when the car stalls when braking on gas. One possible reason could be a malfunction. fuel pump or clogged fuel filter. In this case, the problem may concern cars with both carburetor and injection ICEs.
You can check the condition of the filter yourself. However, only if you have a carbureted car. Each car model has a different location for the filter, but usually it is located in the gas tank area. For diagnostics, you need to get it and check for contamination. Or if it's time for a replacement (by mileage) - it's better right away change it. For injection machines, the filter must be changed regularly, since its visual diagnosis is not possible.
In injection cars, during braking, the ECU gives a command to not supply fuel to the system. However, when resuming work, if the fuel pump is faulty, problems may arise with the supply. If the fuel filter is clogged, then the fuel pump does not have enough power to supply the required amount of fuel to the internal combustion engine, which causes a loss of traction. Diagnose breakdown of the fuel pump on the injection engine can be done by checking the pressure in the fuel line with a pressure gauge. You can find pressure ratings in the manual for your car.
If you have carburetor internal combustion engine, then to check, follow the algorithm below:
- Disconnect the fuel outlet hose from the pump (remove the clamps).
- Try to prime the pump using the manual pump priming lever.
- If it is in good condition, then fuel should come out of the hole (be careful when checking, so as not to get dirty yourself and not fill the engine compartment with gasoline). Otherwise, the pump must be dismantled for further diagnostics.
- next you need to check the suction pressure at the inlet of the fuel pump. To do this, disconnect the suction hose, and use the mentioned lever to start the pump, after closing the inlet with your finger. With a working pump, a vacuum will be created at its inlet, which you will certainly feel. If it is not there, the pump is faulty, it must be removed and diagnosed additionally.
Depending on the degree of damage, you can repair the fuel pump. If it cannot be repaired, you should buy and install a new one.
If the idle speed sensor is faulty
The idle speed sensor is designed to transfer the internal combustion engine to idle mode, as well as to maintain its constant speed. In the event of its failure, the internal combustion engine loses its speed and simply stalls. Diagnosing its breakdown is quite simple. This can be understood from “floating” engine speed at idle. This is especially active when you sharply press and release the accelerator pedal.
To diagnose the device, you will need a multimeter that measures DC voltage. The first step is to check its control circuit. To do this, disconnect and remove the sensor. After that, we connect one contact of the voltmeter to the ground (body) of the car, and the second to the supply terminals in the block (for each car, these terminals may differ, so you must first study the electrical circuit of the car). For example, at car VAZ 2114 you need to connect the tester to terminals A and D on the block. then turn on the ignition and see what the tester shows. The voltage should be around 12 V. If there is no voltage, the sensor control circuit from the computer is most likely broken. It could also be an ECU error. If the circuit is in order, then proceed to check the sensor itself.
To do this, using a tester, you need to check the resistance of the internal windings of the sensor. Again, depending on the design, you need to connect to different contacts. On the same WHA 2114 you need to check the resistance between terminals A and B, C and D. Its value should be 53 ohms. After that, check the resistance between A and C, B and D. Here the resistance should be infinite. Unfortunately, the sensor cannot be repaired, it only needs to be replaced.
Scheme IAC VAZ 2114
Stalls when braking on gas
If your car installed HBO without its own electronic control unit (namely, the second generation), then the probable cause in the operation of the internal combustion engine may be incorrectly tuned gearbox. For example, this situation may occur at high speed when you press the brake pedal and release the gas pedal. In this case, the throttle is closed, and the flow of oncoming air leans the mixture. As a result, the vacuum mechanism of the gas reducer supplies a small dose of gas at idle, and the oncoming air flow also depletes it more. You can fix the problem by reconfiguring the gearbox to idle, in order for the system to supply more gas.
also one possible reason for the situation described above in cars with LPG is clogged filter on solenoid valve (however, it is not available on all installations). To fix the problem, you need to clean or replace it. If there is an adjustment for the position “summer” and “winter”, the filter must be set according to the season. Otherwise, the oncoming air flow can also lean the mixture.
Other reasons
also one possible reason why the car stalls when braking could be throttle valve clogged. This is due to the use of low-quality gasoline, which is so common at domestic gas stations. Due to its contamination, the damper cannot normally participate in the formation of the correct air-fuel mixture, due to which it turns out to be too rich. In this case, it is recommended to remove the throttle assembly and clean it with a carburetor cleaning spray.
In injection ICEs, the reasons for stopping the ICE during braking can be “burnt” nozzles. During heavy braking, they do not have time to close completely, which is why the candles are filled with fuel and the internal combustion engine stalls. In this case, you need to clean the injector. This can be done in different ways - with the help of cleaning additives, dismantling them and washing them in an ultrasonic bath. However, it is recommended to delegate such procedures to the masters at the service station.
In a situation where the car starts to stall when braking, you need to check the integrity of the high-voltage wires. you should also check the quality of the contact on the negative wire from the battery to ground. It's a good idea to check your spark plugs. you also need to know that if there is poor contact on the batteries, then when you press the brake pedal, the internal combustion engine will stall. Accordingly, check the contacts. However, this can only be used for verification. errors in the operation of the computer are also possible, but it must be checked at the service by computer diagnostics.
The most common reasons why it can stall when braking
Hack and predictor Aviator
The most common reason that the car stalls when braking is a breakdown of the "vacuum". Therefore, the diagnosis must begin with its verification. Although In reality, there can be a lot of reasons for the above problem. If you followed our recommendations, but as a result of the checks did not find out the reason, we advise you to seek help from the masters at the service station. They will carry out a complete diagnosis of the car and perform repairs.
