6 Signs and Symptoms for Engine Misfires (& 7 Other Common Causes)

Are you concerned that your car might be having problems? If you’re like most drivers, you probably don’t think about the inner workings of your car until something goes wrong.

And if you’re unlucky, one of the things that go wrong is that your engine starts misfiring. But what is a misfire, and how can you tell if it’s happening to your car?

In this post, we’ll discuss the symptoms of an engine misfire, what it is, as well as some common causes. Continue reading to find out more.

Car engine misfires symptoms

Most common signs of an engine misfire are rough acceleration or idle. A check engine light or poor engine performance are other signs that you might notice. You might also notice the check engine lamp blinking in the middle of misfires.

These are not the only signs that you will see, but they do represent some of the most frequent symptoms. This is a detailed listing of common engine misfire symptoms:

1. Rapid Acceleration

A misfire can cause you to feel an intense jerk or lightening coming from your engine.

This is often caused by engine load, especially when acceleration is hard. Misfires are most commonly seen in high gears with low RPM and the accelerator at the floor. If your engine has a rough acceleration, it is likely that the problem is serious.

2. Rough Idle

The engine can sometimes misfire when it is idle. Also, your engine sensors may get wrong values. Air-fuel mixtures will also be affected. The engine can also experience an uneven idle. It can fluctuate between high and low and may even shut down on its own.

Small air-fuel mix problems in the engine are most noticeable at idle. Therefore, this will likely be one of your first signs that you have misfired.

3. Vibrations

Car engines are very well balanced at the time of manufacture. Balance axles can be added to reduce vibrations.

If one or more of the cylinders isn't firing correctly, it can lead to engine unbalance, which could cause vibrations in your cabin, either at idle or acceleration.

4. Verify Engine Light

Modern cars are capable of monitoring all sensors and functions on their engines. The engine control unit will receive information from the sensor that has detected an issue with the engine.

After receiving the data from the engine control unit, the engine control will make a decision about whether the problem is severe. The engine control unit will indicate if the problem occurs repeatedly by lighting up the check engine lamp to let you know that it is urgently needed.

It is common for the ECU to detect misfires and turn on the engine light. The ECU will also store the trouble code in the cylinder that caused the misfire. The diagnostic scanner can check the codes.

5. Slow acceleration

We have already discussed how O2 sensors can be misinformed and produce a mixture that is too rich or lean.

Overly lean or rich mixtures can cause lowered acceleration and even put your car into limp mode, which will cause the vehicle to not rev over 3500 rpm’s, and it will shut off the boost pressure from the turbocharger.

6. Engine Sound Changed

You may have heard the difference between different engine sounds if you are familiar with cars. A V8 engine produces a different sound than a 4-cylinder engine.

Your 4-cylinder engine may be misfiring on one of its cylinders, making it sound more like a 3 cylinder engine. If your car’s sound is extraordinary, it’s most likely misfires on every cycle that you can hear.

Seven Common Reasons Engines Misfires

Misfires are most commonly caused by a defective ignition coil or poor spark plug. You can also have misfires due to fuel issues, such as a defective fuel injector and a poor fuel pump. It can sometimes also be caused by low engine compression in very rare circumstances.

This is a detailed listing of some of the common reasons I've found over the years working with cars. Let’s begin with the most common reason:

1. If You Own an Old Car, Bad Ignition Coil/Distributor

When it comes to misfires, the most prevalent problem is with the ignition coil. Some cars use a different ignition coil for each spark plug. Others have one coil that has a sparking wire to each sparkplug.

In older cars, there is a distributor, and sometimes an ignition coil. You can remove spark plugs from a car to check if they are separated.

If you notice an ignition coil that is defective or has a trouble code, replace it.

2. Bad Spark Plug

Poor spark plugs is the second-most common reason for a misfire. Spark plugs are what ignite your engine, but they may wear over time. The spark plugs can be very inexpensive and easy to replace.

If you can’t remember the last time you replaced your spark plugs, it’s probably time to replace them. Check out Spark Plugs symptoms to find out more.

3. Leakage intake manifold gasket

Spark plugs can also suffer from intake leaks around the cylinder heads. Older cars that didn't have steel gaskets were more likely to experience this problem.

This is why you should check your older engine. You might also want to check for other leaks, especially if your car is newer. Check for broken vacuum hoses.

4. Low pressure

A faulty fuel regulator, defective fuel pumps, or a blocked fuel filter could all cause low fuel pressure. A low fuel pressure can cause an engine to have a poor mixture, which could lead to misfires in all cylinders.

You should check your fuel pressure if you are experiencing trouble codes that indicate misfires in all cylinders. The causes of low fuel pressure can be found in the following article: Low fuel pressure.

5. Injector Problem

Injector problems are another problem that is more prevalent than five years ago. Faulty fuel injectors can cause misfiring, which is difficult to identify without flow testing.

Newer vehicles are less likely to have injector issues. However, it's worth looking into the possibility of other causes.

6. Low compression/Damage inside the Engine

After you've checked all the other factors, it is possible that your engine may have low compression or some other problem.

Also, misfires could be caused by a faulty timing belt adjustment. Double-check that your timing belt adjustment was done correctly if the belt has been replaced.

7. Wrong Air-fuel Mixture

Sometimes, a bad mixture of air and fuel can cause misfires. A faulty mixture of air and fuel can be caused by many sensors, including the O2 sensor, MAF sensor, and Coolant Temperature sensor.

What's an engine misfire?

Engine misfire refers to a problem where one or more cylinders of an internal combustion engine fail to ignite or fire properly. It can lead to a number of problems, including a loss in engine power and even damage.

We need to first understand what an engine misfire is. You will be able to see how your crankshaft, pistons, and crankshaft move within the engine's cylinder while it is running. A blast inside the cylinder causes the pistons to fall.

The crankshaft spins when the piston is pulled down. The engine is working in four steps; that’s why this engine type is called a four-stroke engine.

1.  As the piston descends, an air-fuel mix from the intake is added to the cylinder.
2.  By pushing the piston up, you compress the fuel mixture with air to create high pressure
3.  In order to ignite the air-fuel mixture, the spark plug's ignition causes the piston to move down. This forces the crankshaft into motion.
4.  The piston moves up and emptys the mixture of burned fuel air and oxygen through the exhaust tube.
5.  Repetition the process starting at step 1.

That’s the function of a four-stroke engine that is fitted in almost all modern car engines.

If one of these stages fails or is missing, it is called a "misfire".

• A mixture of air-fuel and fuel that is either too lean or too rich
• Bad ignition spark / Wrong timing of the ignition spark
• Low compression / Leakage of Air-fuel combination
• It is incorrect to time the intake/outlet for the mixture of air and fuel.

With that knowledge, it’s a lot easier to find the problem that is causing your misfires. You can see that there is not much to misfire in theory.

However, diagnosing your vehicle can be difficult.

Misfire FAQs