ignition coil symptoms

Symptoms of a Bad Ignition Coil & Replacement Cost

In Engine by Magnus Sellén2 Comments

ignition coil symptoms

With a faulty or damaged ignition coil, your car engine can suffer from sudden stalling or hard starting conditions.

An ignition coil is a transformer that is used to convert and supply enough current to the spark plug to produce a spark and start the engine. It is a key component of the car’s ignition system, and if it is faulty, your car will not start.

In this article we will look at the symptoms of a bad ignition coil and examine what preventive measures could be taken to ensure a long life of the ignition coil.

The Function of the Ignition Coil

The purpose of the car’s ignition system is to generate a high voltage from the car battery and transfer this voltage to the spark plugs. With the help of this voltage the spark plug will ignite the fuel-air mixture and start the engine.

The ignition coil is basically a high voltage, a low current transformer that takes voltage from the car’s 12 volt battery and converts it to 25-30,000 volts, which are needed by the spark plug for ignition.

Signs of a bad ignition coil

The most common symptoms of a bad ignition coil are misfires. Misfires can cause further damage to other parts such as the catalytic converter or the O2 sensors. Misfires must be repaired as soon as possible to avoid damaging other parts.

Modern engines have several spark plugs on each cylinder, and each spark plug has its own ignition coil. Each ignition coil is connected either directly or via cable. There are some common problems that occur when the ignition coil is defective, and we will look at some of them here:

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1. Check Engine Light

The check engine light illuminates if there is a problem with the engine. As the ignition coil has a direct effect on the functioning of the engine, the check engine light starts to flash if there is a problem with the coil. If you have noticed any of the symptoms below along with the check engine light, the problem is most likely with the ignition coil.

2. Engine Backfires

Engine backfiring is noticed in the early stages of an ignition coil failure. Backfiring occurs when there is unused fuel in the combustion cylinder and it flows through the exhaust pipe. This also causes black smoke to escape from the exhaust pipe and a bad smell of gasoline, indicating that there may be a problem with the ignition coil. It is recommended that this problem be corrected immediately to avoid damage to the exhaust system.

3. Engine Stalling

If you are driving at normal speed and after a few kilometres you notice that your engine stops, there is a possibility that the ignition coil is defective. An engine stall occurs when the ignition coil delivers irregular current to the spark plug. If it is not repaired immediately, your car may come to a complete stop after a few miles.

4. Poor Fuel Economy

Due to a defective ignition coil, more power is supplied to the spark plug, causing the engine to consume more fuel. This reduces the mileage efficiency, indicating that the ignition coil needs to be checked.

5. Loud Engine Noise

A defective ignition coil does not generate enough voltage for the spark plug, so the engine works harder than usual. This leads to excessive engine noise and vibration.

6. Car Does Not Start at All

A damaged or faulty ignition coil can prevent the engine from starting completely. If you hear a clicking sound when starting the car, the problem is not with the ignition coil. However, if there is absolutely no sound, there is a possibility that the ignition system has failed.

ignition coil

Single Cylinder Ignition Coil

Testing an Ignition Coil

An ignition coil can easily be tested with a digital 10 megaohm impedance ohm meter if you are somewhat familiar with car electronics.

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Connect the two test leads of the ohmmeter to the positive and negative terminals of the ignition coil. The average reading is slightly between 0.4 and 2 ohms. If the ohmmeter shows no resistance, this means that the coil is short. In contrast, a high resistance value indicates an open coil.

Another good way to check the ignition coil is to use a spark tester. A spark tester is available on Amazon at a reasonable price. To check the ignition coil, switch off the engine and remove the coil from the spark plug. Connect one end of the spark tester to the top of the spark plug and another end to the coil outlet.

Once the spark tester is in place, start the engine to check if a light on the spark tester is flashing. If this is the case, the ignition coil is working effectively while no light indicates that either the ignition coil or the oil control circuit is damaged.

If you are interested in purchasing such a device at home, you can check it here on Amazon:
Spark Plug Engine Ignition Tester
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ignition coil long

Ignition Coil Pack

Replacing the Ignition Coil

Once you are sure that the ignition coil is defective, it is time to replace it. The replacement can be done at home, provided you have the right tools. Follow these steps to properly replace the ignition coil:

Step 1: Disconnect the car battery by removing the negative terminal. You will need a suitable socket or wrench to loosen the screw.

Step 2: Locate the ignition coils, which are normally located on the top of the engine and attached to the engine block.

Step 3: Remove the old ignition coil using a socket wrench and also disconnect the electrical connections from the coil. In some cars it is necessary to first disconnect the electrical connections and then remove the coil. For more information, refer to the instructions in your car owner’s manual.

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Step 4: Install the new ignition coil and make sure that all bolts and screws are tightened sufficiently. Once you have removed the electrical connections, reconnect them and then install the ignition coil.

Step 5: Reconnect the negative terminal of the battery.

Step 6: Start the car and take it for a spin to make sure there is no idling, stalling, or engine failure.

Ignition Coil Replacement Cost

Changing the ignition coil is easy, but if you don’t feel comfortable doing it yourself, go to the car mechanic and let the experts do the work. The average cost to replace the ignition coil is between $150 and $270, and the ignition coil itself costs about $120 to $160.

Hello I'm Magnus, the owner and the writer of this website. I have been working with cars since I was 16 and I'm specialized with in-depth Automotive diagnostics. Also been driving drifting for the last 6 years. I'm here to give you answers to all your automotive questions and I hope that you enjoy our content.

2 thoughts on “ Symptoms of a Bad Ignition Coil & Replacement Cost ”

Comments
  1. I have a 2010 Hyundai Elantra with only 71,ooo kms. It started running rough 2 years ago. No check engine light. I cleaned the MAF sensor, throttle body sensor, IAC idle motor and replaced the plugs that seemed ok except a little black. I had the engine motor vacted , exhaust tale pipe has no carbon. Still have a rough idle. When the outside temperature is colder and I out the engine under load it is worse. It does improve after the engine warms up, but still not smooth like it was. Sometimes it seems like it is missing going up hill . It drives ok except sometimes. I still have no solution. I had a autel scanner that showed the short term fuel trim was taking some fuel away because eof a rich condition but the long term fuel trim is close to 0. Both fuel trims together look good. All other live data from the scanner look normal.. I am still lost finding this problem . It use to idle so smooth you can not feel it while idling. Now you can feel it in the steering wheel and car body. Can you help! Thanks Ed

  2. I just had my coils replaced in my Ba Ford it was driving really well now seems to be smoke coming out of the exhaust is this normal

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