We’re sure most of you, at some point in your car’s life, have had to take your car to a repair facility because the check engine light was flashing and the vehicle was not running as smoothly as normal.
When this happens, the engine misfires and the computer tells you to shut the vehicle off before something is damaged.
Today, we’ll explore what a misfire is, why it occurs, and how to react appropriately if it does.
When one or more of the cylinders is not producing power because there is a lack of detonation in that cylinder, that is known as a misfire.
However, to explain what a misfire is and what causes it, we’ll quickly explain how a basic engine works.
For an engine to run properly, it needs air, fuel, spark, and compression.
Think of each cylinder as a container.
Air and fuel are injected into the cylinder through valves on the top of the engine. The piston moves up to compress the fuel and air mixture, which is then ignited by a spark, shooting the piston down with a big bang.
The piston then comes back up to expel the burnt gases.
When you line up multiple cylinders and attach the pistons to one common crankshaft, all these detonations will produce enough power to rotate the crankshaft.
When the piston moves down, it sucks air into the cylinder, which travels from the outside of the car through the air filter, into the intake manifold, and finally into the engine.
The amount of air is measured by an air mass or manifold absolute pressure sensor.
If air is restricted (clogged air filter or inlet), unmetered air sneaks past the sensor (vacuum leak), or if the sensors themselves are defective, it may cause a misfire.
Without fuel, the engine simply will not run. So, a fuel pump will only cause a misfire if it supplies enough pressure to start and run the car but fails to deliver enough fuel under load.
In most cases, fuel-related misfires are due to a faulty fuel injector. Compression requires the cylinder to be sealed airtight.
After fuel and air are inducted, the piston compresses it into a dense mixture. If the cylinder isn’t airtight in any way after the valves close the mixture will leak out and will not combust.
leaking head gaskets, cracks in the cylinder head or block, worn piston rings etc.
The spark ignites the mixture. If the spark plugs are too worn, or the ignition wires or ignition coils have issues then it will not deliver the spark when it is needed.
Now that you know the basics, you’ll have a better idea of what’s going on in your car if ever this should happen to you.
But believe it or not, misfires can actually be more complicated than this to diagnose.
One last thing, all these cycles that occur in order for the engine to run have to be synchronized.
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