Common Signs of a Faulty Ignition Coil

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Common Signs of a Faulty Ignition Coil

When a car functions properly, it drives smoothly and fairly silently. Stalling, low engine power, backfiring, engine noise, and difficulties getting the car started are clear signs that something is amiss. Because ignition coils supply power to the car's spark plugs, a faulty coil can cause any of these symptoms. If the broken coil is not replaced, it can cause long-term damage to the car's engine and exhaust system. Therefore, it is important to pay attention to signs of coil failure and repair the damage before the problem becomes more serious.


Ignition coil overview

The ignition coil is responsible for starting and supplying power to the car. The car battery supplies the power that starts up the engine, but it is much too weak to power the car's ignition on its own. The ignition coil boosts the battery power to a high enough voltage to activate the spark plug and start up the combustion engine.

Some vehicles contain a single ignition coil, whereas others contain multiple coils. Additionally, some engines supply each cylinder pair with its own ignition coil. Multiple ignition coils are usually contained in a unit called an "ignition coil pack". Only petrol engines use ignition coils; diesel powered vehicles use compression to start the engine's internal combustion process.


Signs of ignition coil problems

When an ignition coil pack is completely broken, the car does not start at all. However, in many cases, a car can still start if it has a single faulty ignition coil. Therefore, it is important to pay attention to other symptoms.

Problems starting the car

Difficulty starting the car is a huge indicator of a faulty ignition coil. When the ignition coil is not working properly, it may not supply enough power to the spark plug. If it takes several tries to get the car started, it may help to test the ignition coil.

Misfiring or backfiring

Backfiring or constant engine sputtering can be a sign that the ignition coil is in poor shape. Backfiring happens when excess or unused fuel seeps through the exhaust system. A faulty ignition coil causes the spark plug to partially ignite, leaving extra air and fuel in the system. Misfiring is a similar issue. When the spark plug does not ignite properly, it can cause the sputtering and spitting, especially when the car reaches higher speeds.


A faulty ignition coil causes the spark plug to ignite irregularly, which can cause the car to shut down when it stops. Although vehicles occasionally stall, frequent stalling is a tell-tale sign of ignition coil failure.

Poor fuel economy

Getting fewer kilometres per litre of petrol can be an indicator of a faulty ignition coil. A poorly functioning coil can cause excess fuel to seep into the car's exhaust system, causing wastage. The car must also compensate for the reduction in spark plug power, which uses additional fuel. Drivers who notice that they are using more petrol than usual, or that their petrol does not last as long as it used to, should check the ignition coils.

Loud engine

A faulty ignition coil causes the engine to work harder, which can make it louder than usual. As several other problems can cause excessive engine noise, this is usually a secondary symptom or indicator of ignition coil failure.

Lack of power

A car that has a faulty ignition coil has less power overall than a fully functioning vehicle. The reduction in power to the spark plug can make it difficult to accelerate the car and supplies the car with less power while it is running.


How to test ignition coils

Drivers can easily test their own ignition coils or ignition coil packs at home using an ohmmeter. An ohmmeter is a device that can measure electrical resistance as well as detect the level of power that the ignition coil supplies. To test, a driver needs to connect an ohmmeter to a coil using the positive and negative terminals on the coil. Primary resistance should read somewhere between 0.4 and 2 ohms, whereas secondary resistance on most ignition coil models should read between 6,000 and 8,000 ohms.


How to buy replacement auto parts on eBay

Sellers on eBay offer a large inventory of replacement auto parts to choose from. Because replacement parts such as ignition coils are tailored to specific car models, it is important to include both your car's model and the part you need in the search terms. Once you have found the ignition coil pack you need, read the item description carefully to make sure it is compatible with your vehicle. It is also important to pay attention to the engine specifications, as this can affect coil compatibility. 

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