Six Signs of a Bad Ignition Coil

If you’re having trouble with your car, the problems may be due to a bad ignition coil. An ignition coil … Continued

If you’re having trouble with your car, the problems may be due to a bad ignition coil. An ignition coil is the part of your vehicle that transforms the energy from the battery to a higher voltage to ignite the air-fuel mixture in the cylinder.

Maybe you are having a hard time starting your vehicle, or your vehicle is losing power when you are on the highway. Here, we explain why this could happen and what could be causing it.

How Does an Ignition Coil Work?

The ignition coil is part of the ignition system of a car. The ignition system consists of the ignition switch battery, the alternator, the ignition coil, the spark plug, and the distributor. The ignition coil does the most important job, which is transforming the low-tension current of the battery to high-tension current. The average car uses a 12V battery, and the spark plugs need about 20,000 to 40,000 volts to ignite the fuel. This is the reason the ignition coil is also known as a compact transformer.

The ignition coil has two windings wrapped around an iron core. Normally, the coils are within a housing filled with oil to act as a refrigerant. The primary winding is the one with the low-tension current and is the outer coil. The secondary winding has far more turns of wire than the primary winding and is the one that transmits the high-tension current. This configuration makes the ignition coil a step-up transformer.

When the 12V current enters the primary coil, it creates an electromagnetic field. Then the current suddenly stops, and the magnetic field collapses quickly. This event induces a high-voltage current on the secondary coil, which is sent to the spark plug or the distributor, depending on the configuration.

Automotive ignition coil

Signs of a Bad Ignition Coil

Car Backfiring

A backfire is a loud noise made by an explosion out of turn on an internal combustion motor engine. It can also happen on the exhaust. When an ignition coil is malfunctioning, it doesn’t send enough voltage to the spark plugs, which leads to incomplete combustion. Incomplete combustion leaves unused fuel that later goes out through the exhaust.

Sometimes this unused fuel explodes before getting out and causes greater damage to the system in the long run. Another cause of this problem could be that the spark plugs are not functioning correctly, or the fuel-to-air mixture is too rich.

A clear sign of this happening is when your car starts emitting black smoke. This is identified by a strong smell of gasoline or fire coming out of the exhaust due to the random explosions. This issue is one that has to be checked immediately or it could lead to serious and more expensive problems to your car.

Engine Misfiring or Stalling

An engine misfiring is when one of the cylinders fires incorrectly or doesn’t fire at all. It can lead to weird cough-like noises, jerking motions, and vibration while the car is idling at a stop sign or light. These are clear signs of a failed ignition coil. Other causes could be issues with the fuel delivery system, spark plugs, and plug wires.

Misfires can occur at any time but are most common at the time the engine is under more load, like when you are accelerating. Also, when a car misfires, it generates more emissions and can ruin other parts, like the catalytic converter. The sensors get faulty and can change the fuel-to-air mixture, creating even more problems like the car slowing down instead of accelerating. 

When this problem is aggravated, the car can shut off on its own. This can happen when you just start your vehicle and try to accelerate, when you stop and suddenly shut it off, while idle, or when you accelerate too fast. This can also be due to a problem with the transmission, the idle air control actuator, the fuel delivery system, or a clogged EGR valve.

Poor Fuel Economy

When you have a car for some time, you can determine its average fuel consumption. If you notice less mileage with the same amount of fuel, you could be dealing with a bad ignition coil. When the spark plugs are not receiving enough power, the system compensates by injecting more fuel. 

Another reason for the poor fuel consumption is that when an ignition coil malfunctions, the O2 sensor does an incorrect read and the system sends more fuel than necessary. Also, having bad fuel injectors can cause fuel leaks.

Engine is Hard-Starting

This is more common for a car with only one ignition coil. Having the whole system depending on one ignition coil is a major problem when it malfunctions, but this can also happen with any other configuration. If more than one spark plug doesn’t receive enough power, the car won’t start at all.

If you hear a clicking noise when you try to turn on the car, the ignition coil is probably still working. However, a bad ignition coil won’t generate any power, and in turn, there would be no spark for the combustion to start.

Check Engine Light Is On

If your car’s engine light suddenly turns on, this could be a sign that something is bad with the ignition coil. An easy way to know what is wrong is to take your car to a mechanic for an OBD-II check. You can also do this yourself with an OBD-II scanner, which you can purchase online or from a local auto parts store. The possible standard diagnostic trouble codes (DTCs) are P0300 through P0312, which are codes for a detected misfiring. Codes P0350 to P0362 are reserved for ignition coil circuit malfunctions.

Leaking Oil 

When an ignition coil is not functioning properly, it can overheat. This can cause the housing of the wire coils to break, and an oil leak will occur. Another cause could be that in the spark plugs, the gap is bigger due to erosion. This will cause the ignition coil to operate at a higher voltage. Because the ignition is working harder, it can easily overheat.

Types of Ignition Coils

  • Conventional: This type of distributor system has been used since the early 1900s. The ignition coil and the distributor together make up the complete distributor system. The battery sends power to the primary coil and when the connection is broken suddenly by the distributor cam, it induces a higher voltage to the secondary coil. Then the distributor cap sends the current to the spark plugs.
  • Electronic: This type of ignition coil function is similar to the conventional coil. However, instead of the distributor cam breaking the connection, there is an electronic system to send a signal and start the ignition. These ignition coils were commonly used in the early 1970s.
  • Distributorless: This system uses one ignition coil for every two cylinders. The ignition coils come in packs or have a few ignition coils together in one unit. This type works a bit differently because it uses a magnetic device to change speeds.
  • Coil on plug: In these systems, each spark plug has its own ignition coil. They incorporate the electronic system from the electronic ignition coil.

Car repairs

How to Test an Ignition Coil

If you want to test to see if the ignition coil of your car has failed, these are some simple steps to do so. 

  • With the car turned off, open the hood to locate the ignition coil. The location will differ, depending on the vehicle’s model. A quick search on the internet should tell you where it is in your car.
  • Remove one of the wires from the spark plug.
  • Remove the spark plug, preferably with a spark plug socket.
  • Carefully attach the wire back to the spark plug you removed.
  • Touch the threaded portion of the plug to any exposed metal on your car.
  • Remove the fuel pump relay or fuse.
  • Have someone turn the ignition key for you.
  • If the ignition coil is working, you should see a blue spark between the threaded head of the spark plug and the metal part you are touching.

Ways to Prevent a Bad Ignition Coil

There are easy ways to keep your car in good shape. For the ignition coil, you should pay close attention to all the parts on the ignition system. Keeping the spark plugs in good shape could go a long way in saving you money on future repairs. You can check the plugs for erosion and make sure they are not worn out due to normal usage.

Also, check the ignition coil itself to make sure the housing is in prime condition and not leaking any oil. Check that the wires of the ignition system are not toasted or in bad shape. Last, but not least, perform maintenance as recommended by your vehicle’s manufacturer.  

In conclusion, a bad ignition coil can cause backfiring, engine misfire, vehicle stalling, engine light turning on, poor fuel consumption, and oil leaking. However, if you take care of your vehicle and perform the required maintenance, you shouldn’t have any problems with the ignition system in general.