Is Your Engine Misfiring? What’s a Misfire? Fix misfire with ignition coil replacement?

Posted by HJL_ADMIN 1 on

Engine misfire is due to incomplete combustion of the cylinders fail so they can't power the car or other several possible causes. This is a serious condition that requires immediate service or diagnosis to the car to avoid a serious car fire or costly expense, but what are the symptoms to look out for before it happens? What are the causes of a misfired engine? And how to engine misfire diagnosis?


Symptoms Of A Misfire

Black Exhaust and Unusual Smells (插入video#37)

The most obvious symptom is when you see black smoke and a strange smell coming from your engine. It may mean that your engine is not running properly or there is a damaged cylinder wall causing fluid leakage. You need to determine the cause of the engine smoke or it may cause the misfire problems sooner or later.

Rough Idling

Sometimes, you may be wondering why your engine jumps up and down and even cause your car to start and stop suddenly. The reason could be fewer cylinders running than normal so the vehicle losses power too or the brief hesitation of power delivery when using gas. You will also start to notice that the car accelerates roughly and slower than usual. This is probably one of the first symptoms you notice the engine misfire.

Sluggish Acceleration

Engine misfires can cause the O2 sensor to receive an incorrect message and produce a mixture that is too rich or too lean. This results in sluggish acceleration, or when you step on the gas, you may experience shaking as your car goes into limp mode, which could put you and other vehicles in danger.


Engine Sound Changes

Usually, a strange noise in the car means there must be a problem that the engine is more important. If you know a little bit about cars, you may notice that different engine problems make different sounds, such as engine ticking noise while idling or accelerating. The coughing, clanking or sputtering sound may indicate that your internal combustion response has been interrupted by a misfire.

In any case, if there is an abnormal noise in the car, you must have it inspected by a professional mechanic.

Check Engine Light

Many modern vehicles have equipped with OBD2 systems, and your "check engine light" will come on when a malfunction or detects a problem with the engine. While it may not be possible to tell you that a misfire has occurred definitively, there are many other factors that can trigger the inspection light as well. But when the light comes on it means your engine isn't running properly, and it's important to diagnose your car as soon as possible to determine the actual cause of the problem

 What Is A Misfire?

Engines rely on cylinders to fire. If cylinders don't work properly or have problems with a component in the system, there's a chance that a misfire can happen when the engine starts or even when the engine is idling. Your engine may fail to start or lose power in the event of a misfire. Usually, the symptoms of a misfire depend on what is causing it. Once the problem is found, the repair is completely simple.


In addition, a misfire can place mechanical load and stress on engine components that may cause other problems later, and may even require in-depth repairs.


Most Common Causes of an Engine Misfire

1.Engine coil problems

When the car misfires, the main reason may be because of the worn ignition coil or the spark plug which is part of the ignition coil system. You can use the diagnose tool to test the ignition coil. If there has a problem, the vehicle will provide a specific error code. Fortunately, the misfire problem may be solved by just replacing the ignition coil that it is also a less expensive solution

  1. Air and fuel misfires

Fuel delivery could fail because the injectors can become clogged with dirt or carbon that may provide little or no fuel to the combustion chamber, and then there’s only air in the combustion chamber. In addition, the oxygen sensor or the mass air flow sensor goes out that causes the air-fuel mixture in the car to malfunction.

These can all lead to misfires due to the wrong air-fuel mixture. Any problem which causes the air or fuel mixture to fail can result in a misfire.


  1.  The air leak

A leak in the car can be a problem. Such as a poorly installed spark plug, or a damaged intake manifold gasket, which can cause air gap issues and throw off the air-fuel ratio. The leaking vacuum lines in the engine can also be a problem that could be compromised or worn down over time. The computer couldn't figure out how much air and fuel to send to the combustion chamber. To repair the problem can cost from $100 to $1000 depending on the cause of the vacuum leak.


  1. Mechanical misfires in the engine

Once the timing chain or timing belt are stretched and lose the necessary coordination, disrupting the internal combustion process and causing the engine to misfire. Other engine misfires are caused by a piston of the cylinder not compressing the air and fuel mixture properly, or a clogged catalytic converter in the exhaust system.

From the ignition coils to the spark plugs, many different issues can cause an engine to misfire. Regardless of the cause, don't ignore these problems which could lead to more damage and expensive repairs.


How to Fix an Engine Misfire

First thing first, diagnosing and fixing Engine Misfiring.

Analyze the engine’s error codes.

When your engine misfires, you can use a scan tool to check for trouble codes in the onboard diagnostic system. Although these codes will not tell you exactly what is wrong with your vehicle, at least you can diagnose what caused the engine to misfire, and it can be repaired faster by the mechanic.

P: Powertrain (i.e. engine and transmission)

From P0300 to P0399 (ignition system control)


These codes can indicate a misfire:

P0300 Random/Multiple Cylinder Misfire Detected

P0301 Cylinder 1 misfire detected

P0302 Cylinder 2 misfire detected

P0303 Cylinder 3 misfire detected

P0304 Cylinder 4 misfire detected

P0305 Cylinder 5 misfire detected

Depending on the number of cylinders you have, the code continues in that order.

P0313 Misfire When Low Fuel Detected

P0314 Single Cylinder Misfire (Cylinder Not Specified)

P0316 Misfire detected at startup (first 1000 rpm)


Based on past experience, we strongly advised you don’t drive with a misfiring vehicle. If your engines misfire while on the highway or surrounded by other vehicles, it is best to tow the car to have inspected and repaired and to prevent further damage as soon as possible that better than having your engine suddenly stall or suffer catastrophic damage from repeated misfires on the road.


Once you have draft ideas about the reasons causing the misfire, next let’s give you some tips for the solution.


Find the leak:

Finding and sealing the vacuum leaks around your intake manifold. Before going through this process, you must take the necessary precautions. If you are not confident enough about this, it is best to contact your mechanic.


The fuel injected motors misfire could be the broken vacuum line. Replacing the bad vacuum line might just make the engine run better, the better way is to let the repair shop for a comprehensive inspection. If the vacuum leak is not the cause, you must move on to other tests.


Check fuel delivery:

First, connect a fuel pressure gauge to the fuel pump test fitting at the end of the fuel rail on the engine. Then use the appropriate pressure specifications with the repair manual to compare the readings taken with the engine idling and follow the RPM specified in the service manual.


If the fuel pressure is inconsistent or too low could happen a misfire on all cylinders. In this situation, you should check whether the fuel regulator is appropriately set, whether the filter is clogged or not, and replace them. But replacing the fuel pump may need to seek the help of a professional mechanic to remove it from the fuel tank.

Check the ignition coil: 

As mentioned earlier, if the ignition coil fails they will provide a misfire code to the scan tool. The way to test the engine coil is by disconnecting the spark plug wire and connecting an Ohmmeter to the top two pins. Compare the resistance you see with your vehicle on an Ohmmeter reading. If it does not match, the bad coils need to be replaced. Anything that causes a cylinder to misfire can trigger a misfire code, so a detailed diagnosis should be made to be 100% sure.


The ignition coil replacement cost is between $168 and $218. And the labor costs are estimated between $51 and $64. Ignition coil price does not include taxes and fees, and it will depend on the make and model of the car or its unique location.

Related coil pack cost and repairs may be required, please expect to pay more.


Compression Test:

First, pull out the fuse that powers the fuel pump, and if you're not sure about that leave it to a professional. Then take apart one of the spark plugs and screw the compression tool into it. Start the engine and check the readings on the gauges, it will stay at the highest point reached. Do the same inspection for each cylinder.

When you remove the gauge you should be sure to reinsert the spark plug each time. If one of the cylinders shows a different figure than the others, the misfire is caused by a lack of compression.

If the numbers are lower in two adjacent cylinders, it could mean that area has a damaged cylinder head gasket and needs to be replaced.


How to Avoid the Engine Misfire

Scheduled maintenance

Regular maintenance and upkeep is the best way to avoid an engine misfire. If the check engine light is on and bad coil symptoms happen. Bring your vehicle to a professional repair shop for misfire diagnosis so they can determine and fix the problem. The last word, don't let a small problem to turn into a snowball!


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