8 Reasons Of Why Your Car Starts Then Sputters and Shuts Off

Car issues can be unexpected and highly frustrating, especially when your car starts, then sputters, and shuts off abruptly, potentially ruining your plans.

If your car starts then sputters and shuts off, there are several components that warrant immediate attention. Among the primary issues are the MAF sensor, fuel pressure regulator, faulty ECM, ignition coils, and spark plugs. Additionally, a bad oxygen sensor or a problematic IAC valve could be to blame if the vehicle stalls while idling.

The good news is that many of these problems are fixable. With the right knowledge and tools, you may be able to address the issue yourself. However, if you’re unsure about the reason for the issue or unable to fix it, it’s best to seek the help of a qualified mechanic.

This article deeply explains the causes why your car starts then sputters and shuts off, and how to fix it.

Causes of Why a Car Starts Then Sputters and Shuts Off

Bad spark plugs or faulty fuel pressure regulator is one of the major reasons for a car to start then sputters and shuts off.

The following are the most common causes of why a car starts, sputters, and then shuts off:

1) Bad Spark Plugs

The engine of your engine generates power due to the combustion of the air-fuel mixture inside the combustion chamber. The spark plug generates a spark to start the combustion of this mixture.

As the piston moves upward and downward in the engine cylinder, it makes the crankshaft and wheel axles turn, which powers the car.

When the spark plug goes bad, the ignition process fails, and your vehicle may shut off. When you try to restart the engine, it might run for a moment, but the poor spark causes frequent misfires, and the engine shuts down soon after.

To keep the engine running smoothly, it’s important to replace the spark plug every 70,000 to 100,000 miles since it wears out over time.

Read More: Causes of Oil On Spark Plugs

2) Bad Engine Control Module

The ECM of your vehicle is used to manage different engine functions. If there is an issue with the ECM, such as a sensor input issue or a software issue, it can affect the performance of your engine and cause stalling.

Read More: Bad ECM Symptoms and Causes

3) Faulty MAF Sensor

The MAF sensor plays a crucial role in your engine as it directly regulates the air-fuel ratio by monitoring the amount entering the engine and sending this data to the ECM (engine control module).

Over time, contaminant accumulation may badly impact the performance of the MAF sensor, leading to inaccurate air measurements and disrupting the proper air/fuel ratio.

When the MAF sensor malfunctions due to contamination, the engine may experience starting issues, followed by stalling shortly after.

How To Fix It:-

To address this problem, you should properly examine your MAF sensor for contamination and clean it using an excellent MAF sensor cleaner.

Additionally, it’s essential to test the sensor to ensure its functioning correctly. If your sensor is bad, it should be replaced with a new one to restore proper engine performance.

4) Bad Fuel Pump 

A bad fuel pump is also one of the common reasons for a car to sputter and shut off. When the fuel pump leaks, it can lead to various issues with the internal combustion process. Your engine requires the right air-fuel mixture to start and run smoothly.

Even a small fuel leak in the fuel pump can disrupt the proper fuel-air ratio, preventing the correct amount of fuel from reaching the engine. This can cause your car to start then sputter, and then shut off immediately.

How To Fix It:-

Fortunately, fixing a fuel pump leak is a relatively straightforward process. You can repair the damages responsible for the leak, which should solve the problem. However, if your fuel pump is worn out or beyond repair, it’s necessary to change it immediately to ensure proper engine function.

5) Faulty Carburetor

The carburetor’s primary purpose is to ensure the proper mixing of the fuel and air in the correct fuel-air ratio for combustion in an internal combustion engine.

When the carburetor becomes faulty, it can lead to an improper air/fuel mixture, causing the vehicle to sputter and struggle to maintain power, ultimately resulting in an engine stall.

How To Fix It:-

To address this issue, properly examine the carburetor for any damage or dirt buildup. If it’s clogged with contaminants, hindering the fuel flow, cleaning it with a carburetor cleaner is a suitable solution.

However, if the carburetor is not working at all, replacement or seeking assistance from a professional becomes necessary.

6) Faulty Idle Air Control Valve

A faulty idle air control (IAC) valve is also one of the major causes of a car that starts then sputters and shuts off. It is responsible for regulating the idle speed of your engine, adjusting it according to the requirements to ensure proper working conditions.

When this valve becomes faulty, it can disrupt the fuel-air mixture, leading to engine sputtering and stalling, especially during cold starts.

To fix the issues related to the IAC valve, you need to properly examine the IAC valve and assess its condition. If found faulty, it should be replaced to ensure the engine operates smoothly and avoids starting problems.

How to Clean an Idle Control Valve

• Find the IAC valve, typically found on the throttle body or intake manifold. Check if it’s integrated into the throttle body for some car models.
• Disconnect the electrical connections and remove the 3 or 4 bolts securing the IAC.
• According to the type of IAC valve, use suitable throttle body cleaner and spray it inside the valve on the spring and actuator.
• Scrub the IAC with a wire brush or old toothbrush until it becomes shiny and turns smoothly if it is spring-loaded.
• Allow the valve to dry thoroughly, then reinstall it in its original position.

Read More: Bad IAC Symptoms and Causes

7) Insufficient Fuel

The primary and evident cause for a car starting, sputtering, and then dying is insufficient fuel in the fuel tank. This usually occurs when there is an insufficient amount of fuel in the fuel rail, leading to a lack of fuel pressure to sustain the engine’s operation.

How To Fix It:-

Constantly inspect the fuel levels in your fuel tank before driving. If fuel is insufficient, add more fuel before driving.

8) Bad Fuel Pressure Regulator

A bad fuel pressure regulator is one of the major causes of why your car starts then sputters and shuts off suddenly. In many vehicles, the fuel pump operates at a high rpm all the time, pumping more fuel than the engine needs. To control the fuel flow, a fuel pressure regulator is installed at the fuel rail.

This regulator regulates the pressure of the fuel circulating through the fuel system.

If the fuel pressure regulator fails, it may get stuck and prevent the additional fuel from returning, leading to increased fuel pressure and a higher amount of fuel entering the combustion chamber.

This excess fuel leads to a rich air-fuel mixture, which causes a strong fuel smell, sputtering, and stalling. This issue is particularly noticeable during idle since the engine requires less fuel at that time, making the air-fuel mixture more affected.

How To Fix It:-

When the fuel pressure regulator of your vehicle goes bad, it requires replacement. In contrast to a bad fuel pump, which can sometimes be repaired or sealed, a malfunctioning fuel pressure regulator cannot be fixed.

You will need to purchase a new regulator and replace the old one with the new device to restore proper fuel pressure regulation and engine performance.

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