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Why is my car engine sputtering? (& How to fix it)

The ride should be smooth, but if you are driving and your car’s engine starts sputtering, the main cause for concern may be a lack of fuel.

However, if the fuel gauge is full, it could be a symptom of other engine problems. For example, a clogged fuel filter could prevent fuel from reaching the combustion chambers.

If the problem is not corrected immediately, it can lead to further engine damage. But what are the causes of a sputtering car engine?

The most common reason your car’s engine sputters is a problem with the fuel system. This may be caused by a faulty fuel filter, fuel pump, or fuel injector. It can also be caused by sparking problems due to bad spark plugs or ignition coils.

Although these are not all possible causes, it is a good start. Here is a more detailed list of the most common causes of car engine sputtering.

8 Causes of a Spitting Car Engine

1. Defective spark plugs

wet spark plug

Spark plugs are essential in providing the necessary ignition for the air-fuel mixture. However, the plugs wear out and can no longer function as intended.

In this case, you will have a large amount of unburned fuel, which causes the engine to misfire and sputter. Spark plugs should be replaced more frequently after a fixed schedule to prevent such things from happening. However, if you haven’t replaced them by then, they should be: Bad spark plugs can cause your engine to sputter.

Remove and visually inspect your spark plugs; If they look old and dirty, it may be time to replace them. You should also consider checking the ignition coils, which could cause the same problems.

2. Clogged fuel filter

Dirty fuel filter

The job of the fuel filter is to filter the fuel that goes to the fuel injectors and then enters the engine. A clogged fuel filter can cause too low fuel pressure in the engine or a clogged fuel injector.

Low fuel pressure will cause the engine to run very lean and as a result, the engine may sputter.

The fuel filter should be replaced after a program and if it has not been done in recent services, it may need to be replaced. Fuel filters are usually easy to replace and don’t cost much.

3. Defective fuel pump

car fuel pump

The same applies to the fuel pump as it does to the fuel filter. If the fuel pump fails, the fuel pressure will drop too low, which can cause the engine to run too lean.

The easiest way to determine this is to install a temporary manual fuel pressure gauge on the fuel pressure rail and check the fuel pressure at idle and when accelerating.

If the fuel pressure is too low, there is definitely something wrong with the fuel filter or fuel pump.

4. Vacuum or intake leak

Cracked engine vacuum hose

If there is a leak around the intake manifold or in the intake manifold pipes, it can cause the mixture to be too lean and cause your car’s engine to sputter at idle.

The easiest way to find it is with an EVAP smoke machine. However, you’re unlikely to have one in your home, so you can also try to find leaks by listening for high-pitched noises around the engine compartment when the engine is idling.

You can also spray soap around the inlet pipes to see if you notice any leaks.

5. Dirty or damaged mass air flow sensor

Maf sensor cleaning

The combustion chamber requires the correct amount of fuel and air. Modern engines have an onboard computer that monitors the flow of these components. Mass airflow sensors ensure that the correct amount of air is supplied to the combustion chambers.

When the sensors become saturated with dirt particles, they can no longer transmit correct information to the ECU. This will cause the engine control unit to spray too much or too little fuel into the cylinders, causing the engine to sputter.

You can clean the mass airflow sensor by removing it and cleaning it thoroughly with an electronic cleaner.

6. Dirty fuel injectors

fuel injectors

Fuel injectors perform the function of spraying fuel into the combustion chambers of each cylinder. It is then mixed with air and ignited by the spark plugs.

The fuel injectors contain small filters that become clogged if the fuel filter is not doing its job properly. This can cause the fuel injector to spray too little fuel into the combustion chamber, causing the cylinder to misfire and the engine to sputter.

These little filters are replaceable and any store should be able to replace them for you.

7. Defective catalytic converter

Clogged catalytic converter

The catalytic converter plays a vital role in removing harmful gases from the exhaust. The catalytic converter becomes clogged if it is too old, and it can also happen that parts get lost inside it, blocking the exhaust path.

This will cause your engine to have too much back pressure, which will cause the engine to sputter.

You can use a catalytic converter cleaner to try to clean the converter.

When your catalytic converter is malfunctioning, you will notice a strong smell of rotten eggs.

8. Faulty oxygen sensors

Oxygen sensor

Most modern cars have an onboard computer that monitors all engine components. Oxygen sensors are connected to this, which are responsible for regulating the fuel in the combustion chambers. A faulty oxygen sensor will cause a rich or lean mixture.

Over time, the oxygen sensors become contaminated with dirt and can no longer transmit the correct information to the onboard computer. This causes them to release too much fuel or too little fuel.

To diagnose oxygen sensors, you need a diagnostic scanner.


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