Without a spark, there won’t be an ignition, and the engine won’t start – that’s just how it is. Now, most drivers know what the spark plugs are all about, but they don’t know the first thing about the ignition coils. However, they’re just as important, and if you’ve got a faulty coil pack, the engine will constantly fail at firing up. In that case, you may even end up damaging the vehicle.

To always have a strong spark and proper ignition, you need to make sure the ignition coils aren’t malfunctioning. So, join me in this how to check for a bad coil pack guide, and let’s see what we can do to fix this! We’ll go over the testing process and also talk about the most common side effects of a defective coil pack.

Faulty Ignition Coil Pack Symptoms

Faulty Ignition Coil Pack SymptomsAs we already figured out, a bad coil pack leads to one of the most frustrating issues – engine misfire. The list also includes a “draggy” crankshaft, poor performance, and low fuel efficiency – some of the most common signs and symptoms. Yes, in many ways, they are identical to the problems that you’ll have when the spark plugs are acting up. In my experience, the overly-loud engine is one of the most confusing side effects.

This can happen at any time of the day, and, unless you’re a pro mechanic, the coil pack will be the last thing that you’re going to suspect. The throttle response can be negatively affected as well. I’m talking about a drop in RPM, especially when you’re trying to “climb” a steep road. Next, the dashboard can also give you signs that the ignition coils aren’t doing their job properly. The Check Engine light might come up.

And, it won’t stay there; instead, the light will be blinking. Sometimes, the gas warning light comes forth instead, even though the car has more than enough gasoline. Last, but not least, when you’re driving around with a bad coil pack, you might see smoke coming out from the exhaust tip. If you don’t fix the problem ASAP, the catalytic converter will probably fail.

Ignition Coil Replacement Cost

Wondering how much you will have to pay to have the coils replaced? Here are the average numbers for the US. Depending on the area/state, a brand-new pack can be yours for 150-200 American dollars. Mechanics, in turn, charge 60 to 80 dollars. However, if you’ve got aftermarket parts (like a new header, cold air intake, and such), the labor cost will be much higher.

Testing the Coil Pack

Testing the Coil PackAlright, now it’s time for us to get down to business. The next list includes five of the most popular testing techniques. Most of them will take very little time and effort. You will, of course, need some equipment for this, but it won’t leave your wallet empty. Besides, you might already have some of that stuff in your garage.

Before we begin, I want to mention that the actual number of ignition coils in the vehicle largely depends on the number of engine cylinders. That’s because, in a regular setup, a pair of cylinders gets one ignition coil (but, they each get their own ignition tower). But sometimes, these terms – ignition coil and coil pack – are used interchangeably, keep that in mind.

Method #1: Visual Testing

The first thing you should do is perform a visual inspection. Go ahead and pop the hood. If the issues with the coil pack are severe, you’ll be able to notice burns, cracks, or even traces of carbon. These signs are very in-your-face and hard to miss. In this situation, the best thing you can do is change the coil pack (and maybe the spark plugs as well if they are also damaged).

Method #2: Ignition Coil Swap

Ignition Coil SwapAs we just learned, each ignition coil only covers two cylinders. So, chances are, the issue is with one of the coils, not the entire pack, and a simple replacement will fix the problem. Sometimes, even trading places with another ignition coil can do the trick. Yes, I’m talking about putting a faulty coil on a different set of cylinders to see whether it is, indeed, messing your entire setup up, or not.

Some folks use the so-called scan tool to check for misfire. Others run the balance test. However, if you ask me, these tests aren’t very accurate. That’s because, say, the drop in RPM (which is at the core of the balance test) can be caused by a long list of different things, including the engine, transmission, header, exhaust, and more.

Method #3: Running a Multimeter

Running a MultimeterWhy not try to check the coil pack’s resistance? This is one of the oldest tests, by the way. For it, you’ll need to buy a multimeter/voltmeter. Plus, find your car manufacturer’s user guide slash specifications. Set the multimeter to ohms, and check the windings inside each coil. If the readings don’t match the manufacturer’s specs, that means the coil needs a replacement.

I do have to warn you, though, that this isn’t a very reliable method either. The reason: you can’t inspect the coils when they’re under pressure, hot, and pushed to the limit. Therefore, even a faulty ignition coil can pass the test with flying colors. I’m not saying it’s useless, of course, but not very precise.

Method #4: Using a Spark Tester

Spark testerHave you ever heard about the spark tester? It’s another tool used to check ignition coils for spark. This isn’t a universal tool, meaning you’ll have to get one that’s compatible with your engine, spark plugs, and coil pack. On the bright side, it’s one of the most accurate methods of checking ignition coils and is available at a very affordable price (5-10 US dollars). So, you need to pull out one of the ignition wires and insert the “boot” (comes with the package) in its place.

Then, you plug the actual tester into the boot – it should make a distinctive clicking sound. The other end of the tester goes into the ignition wire. Next, just start the car’s engine, and if there’s a strong, steady spark, you’ll see a blinking light on the tester. If there’s no spark, the light won’t come up. This tool can be used to check the entire ignition system, not only the coils.

Method #5: The Oscilloscope Technique

Last, but not least, we can monitor the ignition patterns using a device called the oscilloscope. I want to say right from the start that it’s pretty expensive, and, unless you know the basics, it can be a bit hard to use. It is the best diagnostics tool, though, and, just like the spark tester, is very well capable of troubleshooting every single part of the ignition system. Look for a scope that includes a detailed manual.


That’s pretty much it for today, folks! Faulty coil packs can cause you a lot of trouble, including engine misfire, poor fuel efficiency, strange noises, and more. The good news is – checking the ignition coils doesn’t require a science degree or pro-grade skills. All that’s required is a set of affordable tools/equipment and some patience on your part – that’s pretty much it!

Follow the provided instructions, and you won’t have any trouble with the testing process. In this guide, we checked out five different coil pack inspection techniques. I’m more than confident that you’ll be able to use at least one of those methods to troubleshoot your coils and bring the car back on its “feet”. Drive safely, take care of your ignition system, and I’ll see you next time!

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