Ignition engine misfire

When your engine is running rough or you have a misfire condition the problem can be a fuel system malfunction. But more often than not I personally have found an ignition engine misfire to be more common than one that is related to the fuel system.

Picture of fuel injectors

Fuel injectors


Yes you can have a problem with a fuel injector that is either dirty or leaking. But in my opinion it’s just not as common as finding a malfunction in the ignition system.

Malfunctions such as a bad spark plug wire or even worn or fowled spark plugs seem to be a more common cause of a cylinder that is not firing correctly.


Checking ignition related misfires

In many of my other articles you may have seen that my first recommendation is to start off with a good visual inspection. Many times you can see a problem such as a rodent chewing through a tasty ignition wire. Ignition system diagnosis should begin with a visual inspection.

Picture of powertrain control module

Powertrain Control Module

You should thoroughly check the entire system for obvious problems disconnected components or even poor connections to things such as ignition coils and modules. Most modern ignition systems are tied into the vehicles power train control module for this reason you should also inspect the connections to the vehicle’s main computer.

In some cases if you have an ignition engine misfire a trouble code will be stored in the vehicle’s computer. In most cases this would also turn on the check engine light. In rare instances the code could be set as a pending code and you would need a scan tool to read and diagnose it.

Often a set diagnostic trouble code can lead you to the cause of the cars problem. In other cases further diagnosis by an experienced automotive technician may be required. If you have an ignition engine misfire in combination with the check engine light the code should be diagnosed and repaired before you move on to further diagnosing ignition system.


Checking electrical connections

The coil and the ignition system require generous amounts of power to produce the high-voltage spark. You should remember to check the condition of the battery and battery connections as well as the starter and solenoid connections. Some automobiles use these connections to branch off as a voltage source for the coil or ignition system.

Picture of PCM grounds

PCM Grounds

Also equally important as power and voltage connections would be the ground connections for the ignition coil and module circuits. On some vehicles multiple ground locations will be used for different functions. Also keep in mind that some vehicles use body panels, frame members and even the engine block as grounding locations.

Both the power and ground side of the circuit where they originate can be susceptible to corrosion and poor connections. When it comes to testing for individual spark to a cylinder I use a ignition spark tester. This is a very effective way to verify that the proper current is being sent to each spark plug. When in doubt a quality auto service manual will provide diagnostic tree charts for the symptoms that you’re having. For more information about this website and additional posts you can visit the online auto repair home page.


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