Not only is it inconvenient, but your car's engine cutting out can be very dangerous, especially when tackling junctions and roundabouts. If you find your car is cutting out regularly, take 10 to read this article, exploring all the possible causes.

Why Does My Car Keep Cutting Out or Stalling?

There are multiple reasons why your car could be cutting out, these will generally fall under the following: an electrical issue (faulty sensor or control module), a fuelling issue (blocked fuel filter or bad fuel pump), or a spark issue (faulty ignition coil or bad spark plugs). 

10 Most Common Reasons a Car is Cutting Out

1. Blockages in the Fuel System 

Your engine needs a constant, uninterrupted supply of fuel to run smoothly. Debris and dirt in your fuel tank or lines can cause blockages that cause stalling or cutting out. 

Another area to check is the fuel filter, this prevents the aforementioned detritus and contaminants from making it to the engine. Over time the filter can become clogged and restrict the flow of fuel.

2. Faulty Ignition Coil Pack

In a petrol car, the fuel and air mixture is ignited by the spark plugs, which are connected to an ignition coil. Older cars tend to have one coil pack for all the cylinders, and others have individual coils, one for each spark plug.

With the heat and vibration present in an engine bay, the coils can break down over time, and fail to power the spark plugs correctly.

3. Faulty Air Flow Sensor

To ensure the correct running of your engine, an airflow meter is used to monitor how much air is entering the engine. If the sensor has become clogged or damaged the ECU will be unable to correctly adjust the fuel input, causing poor running and stalling.

Issues with air flow meters don't always require immediate replacement, they can often be removed and cleaned to resolve the problem. 

4. Faulty Fuel Pump

An integral part of the fuel system is the pump that moves fuel from the tank to the engine, they are electronically powered and can sometimes wear out or fail. In this case, insufficient fuel will be delivered to the engine, naturally causing running issues.

5. Faulty Sensors

Alongside the air flow sensors, ECUs use many other sensors to monitor the state of an engine, these include cam position sensors, crank position sensors, knock sensors and manifold pressure sensors. 

As sensors are often exposed to high levels of vibration and elevated temperatures, they can break down over time and produce erroneous or incomplete data to the ECU. 

6. Worn Spark Plugs

A petrol engine requires air, fuel and an ignition source. Ignition inside the cylinder is provided by a spark plug. Over time spark plugs can become worn and deteriorate, reducing the strength of the spark, and therefore the efficiency of the engine. 

In extreme cases very old spark plugs can cause stalling or idling issues, the colour of the spark plugs can indicate if worn spark plugs are the cause of the problem.

7. Idle Control Valve

Some older cars at idle, i.e. when there is no accelerator input from the driver, use an Idle Control Valve to keep the engine ticking over with a low enough RPM to not stall, but not excessively waste fuel. 

A sticky or worn Idle Control Valve can cause an engine to stall, this is especially common to happen when slowing down to a stop, such as at a junction or traffic lights. 

8. Damaged Wiring

There are numerous electrical systems that control the running of an internal combustion engine, including ignition timing, fuel supply and the management of both combined. 

Any damage to the wiring loom can cause erratic running and stalling issues, which can also often occur at irregular intervals.

9. Faulty Battery and Alternator

The systems mentioned above naturally require electrical energy to operate, this is provided by the car’s battery, which is topped up whilst driving by the alternator. 

Issues with either the alternator or the battery can cause running issues, by interrupting the power supply to the ECU, ignition coils or various other systems.

10. Empty Fuel Tank

As obvious as it sounds, it's surprisingly easy to run out of fuel, this can either be caused by a faulty fuel level sensor, meaning the gauge is showing the incorrect level, or of course a distracted driver!

If your car is a diesel, you may need to have the fuel system bled before it will restart, as there is likely to be air in the fuel lines. 

How to Avoid Car Stalling Issues

Regular servicing and maintenance can identify issues such as worn-out spark plugs, coil packs or blocked fuel filters. Having this done can mean any future stalling issues are both less likely to occur and easier to diagnose and fix.

Repair Stalling Issues Easily With Bumper

Some of the most common issues we’ve discussed above can mean unfortunately timed bills, to ease the inconvenience of these, Bumper offers zero-interest financing on car repairs, offered by hundreds of our approved partners across the country.