What is causing my car's engine to sputter? What to do?

Driving should be smooth, but if you drive and your car’s engine starts sputtering, the first cause of concern may be low fuel.

But if you notice that your fuel gauge has become full it may be an indication of other engine issues. Unblocking the fuel filter can prevent fuel from entering combustion chambers.

Failure to correct the problem immediately can result in engine damage. However, the question is: What causes a sputtering engine in a car?

Fuel system problems are the main reason that your car's engine sputters. Bad fuel filters, fuel pumps, and fuel injectors can all cause sputtering. Spark issues can be caused by bad ignition coils or spark plugs.

While these are not all the possible causes, it’s a good start. Below is a list that explains the main causes of engine sputtering.

Eight Causes for a Sputtering Car engine

1. Problems with spark plugs

Spark plugs provide the ignition necessary for air/fuel mixture. But, over time, the plugs can wear and stop working as they were intended.

This will cause the engine to misfire and the fuel tank to be full of unburnt fuel. It is important to replace spark plugs on a set schedule in order to avoid such problems. However, if you haven’t replaced them at the time, they should be – faulty spark plugs can cause your engine to sputter.

Take out your spark plugs, and inspect them visually. They may look old or dirty. It is also worth checking your ignition coils as they could be causing the problem.

2. Fuel filter clogged

The fuel filter‘s job is to filter the fuel going to the fuel injectors and then enter the engine. Unclogged fuel filters may cause low fuel pressure in the engine or clog fuel injectors.

A low fuel pressure can cause your engine to run extremely lean, which could cause it to sputter.

The fuel filter should be replaced after a schedule, and if you haven’t done so during the last services, it may need a replacement. The fuel filter is usually easy to change and doesn't cost much.

3. Failure Fuel Pump

Similar principles apply to both the fuel pump and the fuel filter. A bad fuel pump will lead to a very low fuel pressure which could cause your engine to run lean.

This can be done by attaching a temporary fuel pressure gauge to your fuel pressure rail. You will then check the fuel pressure at idle and rev up.

Low fuel pressure can indicate a problem with the fuel filter, or fuel pump.

4. Vacuum the intake or leak

A leak at or around the intake pipes can lead to an insufficient mixture. Your car's engine will sputter when idle.

Using an EVAP smoke device is the best way to locate leaks. It is unlikely that you own one, so you might also be able to listen to the high-pitched sounds around your engine bay while it idles.

To check for leakages, you could spray soap on the intake hoses.

5. Sensor for mass airflow sensors that are dirty or damaged

It is essential that the combustion chamber has enough fuel and sufficient air. The modern engines are equipped with an electronic computer to monitor the movement of all these parts. Mass air flow sensors make sure that combustion chambers are supplied with the correct amount of air.

When the sensors get saturated with dirt particles, they can no longer relay the ECU’s right information. The engine control unit will spray excessive or insufficient fuel into the cylinders. This can cause it to start sputtering.

Clean the sensor mass airflow by unplugging it, and then cleaning it carefully with an electronic cleaner.

6. Fuel injectors that are dirty

Each cylinder's combustion chambers have fuel injections that spray fuel. These fuel injectors then mix the fuel with air, and in turn ignite it using spark plugs.

Small filters are located inside the fuel injectors. If they're not working properly, it can cause them to become blocked. The fuel injector may spray too much fuel into the combustion chamber. This could cause misfiring and engine sputtering.

The small filters can be replaced by any shop that is equipped with the necessary tools.

7. A defective catalytic convertor

Catalytic converters play a crucial role in the removal of harmful gases from exhaust. It can get clogged when it becomes too old. Also, it may lose parts which could block the exhaust.

You will experience excessive backpressure in your engine. This can cause it to start sputtering.

A catalytic cleaner can be used to clean the converter.

You will smell rotten eggs if your catalytic conversion isn't functioning properly.

8. Sensors with low oxygen levels

The majority of modern automobiles have an onboard computer which monitors the various engine components. This computer is connected to oxygen sensors, which are responsible in regulating fuel flow into combustion chambers. An oxygen sensor that is not working properly can cause an excessively rich or low-quality mixture.

The oxygen sensors can become dirty over time and are unable to relay correct information to their onboard computers. They can then release excessive or insufficient fuel.

You will need to use a scanner in order to identify the oxygen sensors.