Engine Misfire Causes Diesel – 6 Main Causes!

Engine Misfire Causes Diesel – 6 Main Causes!

January 24, 2024 0 By CarGuy

Are you experiencing engine misfires and you wonder which are the engine misfire causes diesel? If that’s correct, you are in the right place because in this article there will be a lot to cover.

Doing good and thorough research on a problem is always a good idea. You just don’t want to rely on greedy mechanics. Especially for some simple problems such as engine misfires. This is why we will try to help you out.

So, what are we going to cover? Well, first we will learn more about engine misfires and how these misfires are represented. Then, we will cover the engine misfire causes diesel and see what could be causing this problem in diesel engines. Lastly, we will learn more about troubleshooting and fixing the problem. So, let’s get started.

What Is Engine Misfire?

One of the first things that many people have trouble with when it comes to engine misfires is what is an engine misfire in general. What is the definition of a misfire?

The answer to this question is simple. This is a situation when you have premature or delayed combustion in a certain cylinder.

All of the cylinders need to fire at the same time. But if one of them combusts prematurely or too late, it means that you have an engine misfire.

So, how these engine misfires are represented in diesel engines? Well, in diesel engines you don’t have a spark plug and coil.

Diesel engines ignite the diesel with the help of compression. The fuel is compressed so hard that it simply ignites by itself.

The symptoms of a misfire in diesel engines can include check engine light, rough engine idle, low engine power, poor acceleration, noises from the engine, engine vibrations, and pops and bangs from the exhaust.

From all these, the check engine light is definitely one of the most reliable sources to learn if you have a misfire or not.

But for this purpose, you will need to connect an OBD2 scanner to your car or truck and read the codes.

Later on in the article, we will learn how this is done. Now let’s take a look a the engine misfire causes in diesel engines.

Engine Misfire Causes Diesel

Now let’s learn more about the causes of misfires in diesel engines. Knowing the causes will easily help you out when it comes to solving the problem in your car or truck. You will know where to look and how you need to tackle the issue. So, let’s dive into the causes.

1. Low Engine Compression

One of the main causes for the engine misfire in diesel engines is the low engine compression.

So, what is low engine compression? Well, this is a situation when the internals of the engine are not sealing properly.

There are engine valves for the intake and for the exhaust and also rings on the pistons. All these components have to seal properly in order to have a good compression ratio.

Usually, these components are worn out and the engine can start to lose compression. Resulting in engine misfires.

So, if you have a very high mileage engine, this is probably the cause for this low compression situation that is causing the engine to misfire.

Another situation that is closely related to low compression is damage to the piston. Diesel engines tend to destroy the pistons. So, there is nothing strange in seeing a piston with a giant hole inside.

Now let’s move to the next causes of engine misfires in diesel engines.

2. Lean Or Rich Air To Fuel Ratio

Another very common cause for engine misfires in diesels is the air-to-fuel mixture ratio. So, what is this mixture?

Well, this is the ideal mixture of air and fuel that should be injected into the cylinders. If the mixture is not properly adjusted, you will face premature or delayed detonations.

These poor detonations are in other words engine misfires. This is why you need to make sure that your air-to-fuel ratio is correct and you don’t have a badly performing engine.

In the following chapters, we will learn more about which things can cause your engine to experience bad air to fuel mixture and engine misfires.

3. Broken Injectors

One of the main causes of problems such as engine misfires that can seriously ruin the air-to-fuel ratio is the injectors.

The injectors are really important for your engine and help your engine work well. If there is an injector that performs poorly you will experience problems with the air-to-fuel ratio.

This poorly performing injector will result in engine misfires. So, if you have a single cylinder that is misfiring, your best bet would be to check the injector and see if this component is in good condition. If not, you need to rebuild it or replace it in order to bring your engine back to normal working order.

4. Poor Fuel Quality

Another cause that can trigger an engine misfire is the poor grade of diesel that you add to your truck.

This situation is also known as pinging, where low-quality fuel is injected and this fuel combusts prematurely and creates problems.

However, this issue is less common in diesel engines and more common in gas-powered engines. But fuel quality can still affect the work of your engine.

If your engine requires premium diesel you should add premium unless you want to deal with these issues.

Now let’s move to the next engine misfire causes diesel.

5. Vacuum Leaks

Vacuum leaks are another fairly common for engine misfires to occur inside of an engine. So, what is a vacuum leak, and why it is a problem?

Well, a vacuum leak is simply unmetered air that goes into the intake manifold of the engine. This is air that was not measured by the MAP and MAF sensors.

This air then when injected into the mixture creates an uneven air-to-fuel ratio that causes engine misfires to occur.

This is why you need to make sure that there are no air leaks from the valve cover or vacuum hoses around the engine.

This way, you will have a good ratio that will not trigger engine misfires to occur and possibly ruin your engine performance.

6. Bad Engine Timing

The last in our list of engine misfire causes diesel is the engine timing. If the timing of your engine is poor, you will experience engine misfires.

So, what do we mean by poor timing? Well, this is the timing between the top and bottom end of your engine.

Valves and pistons need to be perfectly synchronized in order for you not to experience such problems.

So, how can engine timing be affected? Well, a couple of things can ruin the timing of your engine. These include broken timing chain tensioners, broken timing chain guides, and stretched timing chain.

All of these things can potentially make the timing chain perform poorly. In some cases, if there is too much slack, the chain can even jump and cause the valves and pistons to collide and engine damage to occur.

Engine Misfire Diesel Troubleshooting & Solution

Now let’s say you have an engine misfire in your diesel engine. How you should diagnose and possibly solve the problem?

Well, the first thing you want is to plug in an OBD2 scanner and let it scan for codes. Only this way you will be sure that you have a misfire and you will know which cylinder is misfiring.

So, if you have only one cylinder that is misfiring, you can do a compression test to see if there is compression in that cylinder.

If there isn’t compression, you found your culprit, this could be because of bent valves, failed piston rings, or cracked piston.

If there is compression, there is probably something else that is causing your problem. This could be a vacuum leak or a bad injector.

In case all of the cylinders misfire, you probably have some internal engine damage like bent valves because of a failed timing chain mechanism, an issue with the fuel system, or a vacuum leak.

Conclusion To Engine Misfire Causes Diesel

Overall, the problem with engine misfires in diesel engines can be very annoying to deal with. But everything is fixable.

The first thing is to find the misfiring cylinder and do a compression test. If the test is good and you have a compression the problem can be caused by a bad injector or vacuum leaks.

If the test is bad and you have a loss of compression, you could have bent valves, failed piston rings, or a cracked piston.


What is an engine misfire?

An engine misfire is a premature or delayed combustion. Every cylinder has to fire in the same order and if there is a premature combustion, you have an engine misfire.

What could be causing engine misfires in diesel engines?

This problem can be caused by a few different things. There could be engine damage. For example, poorly sealing compression rings, bad engine valves, or a cracked piston. But this problem can also be caused by other things like failed injectors or vacuum leaks.

How to fix an engine misfire in diesel?

The first thing you need to do is to locate the misfire. With an OBD2 scanner, you will be able to learn the codes. For example, if you have a misfire and an injector code, then the solution is simple, it is probably the injector. If there is only a misfire, there can be different causes, such as low compression or vacuum leaks.