What is a Misfire on an Engine?

what is a misfire

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It is frustrating when our car is misfiring. The jerking and vibrations give us a feeling that the engine is going to stop working any time soon and so we have to keep pressing the accelerator. Having a smoother, clean engine is peace of mind and it is always better to inspect the vehicle and fix problems if it was not smooth lately. Besides, the engine repair costs are very high and it is wise to avoid that at any cost.

Most of the time a misfire is caused by minor problems in the ignition system which can be fixed without emptying our pockets. It can vary from spark plug issues to ignition coil issues and can be repaired ourselves. The key is finding out the underlying reason why the car is misfiring. Let us help you understand more about misfires right from what is a misfire to the various reasons that can cause it.

What is a misfire?

The car engine works on the energy delivered from the combustion of air-fuel mixture inside the combustion chamber. The fuel is mixed with air in the fuel injector (or carburetor in older cars), which reaches the combustion chamber. The spark plug provides the spark required to burn the mixture, and thus energy is transformed to mechanical energy.

An issue in any of the steps leading to the combustion can cause what we call as ‘misfire’. It just means that the combustion was not perfect. It either missed one, or was not complete, which results in the jerking, vibrations or loss of power.

Reasons behind engine misfires

1. Issues with the ignition system

The ignition system consists of the alternator, ignition coil, spark plugs, etc. These are the components that are responsible for creating sparks on the spark plug, the end product of the ignition system. If the ignition system is causing it, you will notice the misfires gradually increasing. The spark plugs are the culprits most of the time.

The spark plugs need periodic cleaning to work smoothly. Carbon deposits can buildup on the spark plug electrodes hindering the sparks, which will result in the spark plugs not providing enough sparks to ignite the fuel and hence the misfires.

Replacing the spark plugs is the best fix, and if you choose iridium spark plugs or platinum spark plugs over the traditional copper spark plugs, you will be able to see a spike in engine performance and mileage as they provide better ignition. They last up to three times longer than the copper spark plugs. Always choose one of the best 27 spark plugs available on the market.

Sometimes, the ignition coils are the culprits. Dirt and dust may accumulate over them, hindering proper functioning, and an ignition coil replacement might be necessary. It is better to leave it to a mechanic, but it can be fixed ourselves, provided we have the tools required.

2. Issues with the fuel system.

The second most probable reason behind misfires is the issues with the fuel system. Fuel system components usually last longer and do not wear out easily, but if the ignition system is fine, it is better to check the fuel system.

The issues can be small or huge. Perhaps the fuel filter or the fuel injector is clogged. In older engines, the carburetor needs periodic cleaning and getting it cleaned might solve the problem. If these are good, check the fuel pump and the mass airflow sensors.

If the misfires started since the last fuel refill, chances are that the quality of the gas is not good. Misfires can happen when the octane number of gas is very low, and refilling with higher quality gas will solve it.

If the problem is with the fuel system, the misfires will start in a short period and it will be severe when idling. On the other hand, ignition system issue grow gradually and the misfires will be severe at highway speeds.

3. Mechanical issues.

Having a misfire due to a mechanical issue is a worst case scenario and unlike other two, this is hard to be fixed ourselves. The intake manifold gaskets, vacuum lines etc. could be in a bad condition or the timing chain might have slipped. It can be due to various other mechanical issues also.

When it is a mechanical issue, the misfires will worsen when the engine is operating at a higher rpm. Your vehicle’s PCM will show a code also.

Whatever be the reason behind the misfire, it is better to fix it sooner since it can grow into bigger problems and will cause serious mileage drops.