It is annoying when you try to slow down the car, but the engine shuts off. It can be an issue of concern if it keeps happening regularly. You need to find the reasons for this and solve them for the optimal performance of your car.
So, why does your car shut off when stopped or slowing down? The problem can occur due to a number of issues, such as:
- AC load on the engine
- Low oil Pressure
- Problem with the fuel pump
- Irregularity in the idle air control duty cycle
- Vacuum leak in the car’s intake system, etc.
Let’s explore these problems and describe how you can solve them. Understanding these problems is crucial for you to experience smooth driving.
Causes Leading to Engine Shutting Off When Slowing Down And Solutions
If your engine dies while slowing or stopping the car, it is often due to a complex problem. Therefore, you need to find the issue as soon as possible.
The most common reasons I have found are discussed below.
AC Load on the Engine
The problem of shutting off your engine can be related to the RPM and A/C load. Check the engine’s idle speed and if the air conditioning is turned on or off.
When you are not driving, but the AC is on, the engine can slow down more when you release the gas pedal. It can result in a shutting off of the engine.
Diagnosis and Solution
In this case, you need to check the clutch on the AC compressor. The clutch can get stuck in case the compressor is damaged. Turn on the AC again and have a look at the compressor. If it is not working, then you need to change the compressor. This will solve the problem for you.
Another possible reason can be a dirty ICV if the problem is not with the compressor. The idle control valve can get clogged by dirt with time. Take the ICV out and clean it properly. Insert the valve again, and hopefully, your problem will be solved.
Low Fuel Pressure
Fuel or oil pressure is crucial for the optimal performance of your car. Your engine needs fuel to keep running. If there is low fuel pressure, the fuel supply will decrease when you slow down the car. Sometimes, the engine may get no fuel at all and stall.
The fuel low pressure can happen for a number of reasons, including fuel pump failure, clogged fuel filters, leaking fuel lines, electrical issues, etc. You must take immediate action if you can identify that the problem is with the fuel pressure.
Look for signs like clunky noises, backfires, trouble starting the machine, and misfires.
Diagnosis and Solution
The problem of low fuel pressure can occur due to several reasons. If you do not have enough fuel in the tank, then refilling will do it. However, sometimes you may have enough oil, but still, there can be low fuel pressure. In such cases, you can do the following things:
- Check the oil pump. If it is not working properly, then you will need to replace the pump.
- Check the rod bearings. If they are worn out, the pistons will not move smoothly. This can lower fuel pressure. You will need to change the rod bearings if they are severely damaged.
- You should also have a look at the oil filter. Clean them properly, as clogged filters can hamper oil pressure.
- Check the manufacturer’s recommendations once again. You need to use the right oil grade to maintain optimal oil pressure.
Check for a Vacuum Leak
A vacuum leak is a common reason for such problems. If there is a vacuum leak in the engine’s air intake system, extra and uncontrolled air can enter the engine. The extra air makes the air-fuel mixture thinner. It will result in weaker and less stable combustion.
You should remember that the engine relies greatly on stable combustion when the car is stopped or slowing down. Because of the vacuum leak, the idle speed is not maintained, and the car comes to a halt.
Diagnosis and Solution
A faulty mass airflow sensor is responsible for a vacuum leak in the engine. This hampers the combustion of the engine of your vehicle. You can detect a bad MAF sensor by symptoms like erratic idling, poor acceleration, stalling at low speeds, engine hesitation, jerking, and an illuminated check engine light.
You need to unplug it from the air intake duct for cleaning. Use a clean cloth or paper towels. You must be gentle while cleaning the device as the sensor is a thin wire and very fragile.
Something Is Wrong With the Fuel Pump
If your car keeps stalling when slowing down, this can often hint at a damaged fuel pump. The pump regulates the circulation of fuel throughout the moving parts of your car’s engine.
A damaged pump cannot provide enough oil to the engine. When you slow down the car, the engine demands less fuel. And your engine fails to do so. As a result, the engine shuts off. Do you hear any sputtering while driving the car? If yes, then there is a high chance the issue is really with the fuel pump.
Diagnosis and Solution
Unfortunately, fuel pumps are complex components and are mostly unrepairable. If there is any issue with the pump, you need to replace it. However, you must look for additional signs of a bad fuel pump, such as high temperature, engine sputtering, power loss, engine misfire, etc.
IAC Duty Cycle
If the problem is not related to any of the above, then you can try adjusting the IAC duty cycle. The IAC duty cycle is a part of the engine that helps control the idle speed of the engine. Your car needs to maintain a minimum speed when it is not moving. Otherwise, it will stall, or in other words, shut off.
Diagnosis and Solution
You can try cleaning the IAC valve with a carbon cleaning product. You will find the valve located on the intake manifold near the throttle body. In some cases, you may have to reset the IAC. Watch this video for visual instructions for this:
FAQ
Here are some of the commonly asked questions that might be helpful for you, too.
Q: Can I repair the fuel pump if it causes my car to shut off when stopping?
Fuel pumps are designed not to need maintenance. When the pump is damaged and causes your car to shut off, the best option is to replace it. Repairing the pump is not safe.
Q: Why does my car shake when slowing down?
Your car can shake when slowing down because of unbalanced tires or wheels, warped rotors, loose bearings, suspension issues, or malfunction in CV joints or axles. You must not ignore the problem as it hints at some serious problems.
You can see several factors that can cause your car to shut off when stopping or slowing down. You should not neglect the problem as the reason can be something vital for your safety.
You must try to find the problem and take steps to solve it. In most cases, the better option is to take your car to a mechanic. Getting rid of the problem is necessary for having a smooth driving experience.