Ignition Coil Pack Problems
How to diagnose fix and replace
If your driving a modern car chances are it has an Ignition Coil pack as it is much more effective than the old distributor system you will find on older cars. These ignition coil packs are great and perform as intended most of the time. They however can go bad from time to time, but you need to make sure its the coil pack that’s faulty and not just the high tension leads or the spark plugs.
In this guide we will show you how to diagnose, fix and replace a faulty coil pack. For a more in depth description on coil packs visit this page.
Rough Idle? Slugish Car? Diagnosing a faulty coil pack
If you have noticed a lack in performance in your car, then a great place to start would be to check your ignition. This involves testing your coil pack, HT leads and spark plugs. Here are some signs to look out for when looking for a bad coil pack:
You should notice a rough idle
The engine may be unexplainably louder-than-usual
There will be a lack of power in your engine most noticeable going up hills
A noticeable drop in RPMs while accelerating.
Your engine warning light will normally flash on and off our come on randomly as the engine misfires.
Some people have noticed that there fuel warning light may come on even though there is enough fuel in the car.
One of the main problems you may notice is puffs of smoke coming out of the exhaust instead of a constant stream of smoke.
The only problem with a faulty coil pack is that they show the same symptoms as a faulty spark plug or damaged HT lead. It’s best to check your spark plugs and HT leads first before replacing a coil pack as this is a less expensive procedure. Chances are though if you have been running a faulty coil pack for a while you should in theory replace your spark plugs, HT leads and coil pack to freshen up the ignition system. See our guide on spark plugs to find out if they may be the cause of the problem.
If you notice any of the above problems and have checked your HT leads and spark plugs and noticed they are not at fault but still have the same problems, well then of course it’s going to be a faulty coil pack. But don’t worry! These are simple to replace!
Replacing A faulty coil pack
So, you have worked out that the coil pack is to blame for the poor performance your getting out of your car. Not to worry this is a very simple fix and shouldn’t take you more than an hour to complete the job. Before you begin make sure you have disconnected the battery.
Tools you will require for the job
With this being a small job there are not many tools required for this job as it really is just a matter of removing a few wires, plugs and bolts that can be achieved with the use of one tool.
Socket set/ allen keys/ torx security tool
The hardest part when changing an ignition coil pack is finding out what tool to get the bolts off. It’s crazy really you would think that everyone would use the same size screw/bolt to attach these damn things to the car (hell no!). Car manufacturers like to be awkward on purpose, you will normally find the coil pack in an awkward position and it will most likely have a torx security screw which are quite fiddly to remove. You will need to double check your car owners manual to find out which tool you need to remove the bolts on your coil pack.
Here are Beat The Mechanic we recommend all potential car DIY users to have a full set of all 3 listed above as you will be surprised how useful they are when it comes to fixing your own car.
replacement coil pack
Make sure you purchase the correct coil pack. Depending on what car you drive you can possibly get by on a refurbished unit or one from a scrap yard on a low mileage car. These are not cheap brand new, so think long and hard before reaching for your card! It would be best to purchase a haynes manual to find out which coil pack you require.
spark plugs – if required
If the spark plugs are fine or near enough new you should not need to replace them but its normally common practice to replace them at the same time you change your coil pack.
HT leads – if required
If the HT leads show no sign of wear or problems then you should not need to replace them, but it’s not odd for mechanics to replace these as part of a full coil pack kit.
Now you have the tools to begin the job we can get on our way!
Changing Your Coil Pack
Now that you have the correct tools for the job and are confident in taking on the job it’s time to begin.
Locating Your Coil Pack
In most cars coil packs can be hard to get to as they tend to be bolted somewhere on the engine whether this be on the left the right or somewhere completely random. The best way to find your coil pack is to follow the HT leads. Locate your HT leads on your engine and follow them. If all wires point to a little black box, well this my friend is your coil pack.
in some cases the coil pack may directly be on the spark plugs so check your car owners manual if you are lost and can’t seem to locate your coil pack.
Removing your coil pack
Before you begin disconnect your battery so you minimize the risk of shock.
By far the hardest part about this guide is removing the coil pack, this varies from car to car. Some cars just require a simple bolt to be removed via a socket set or allen key others like the Renault Clio require you to remove 4 screws that are screwed in by torx security screws and placed in an awkward location making it quite hard to turn the bolts. Alot of profanities where used when removing one of these! Mainly down to dropping the torx tool in the car and having to fish it out again.
Before removing these screws get a pen and piece of paper and take note of where your HT Leads are attached to the coil pack. YOU DO NOT WANT TO MIX THESE UP – This will lead to a misfiring engine or something worse, so it’s best to keep note. You can use a white pen if needed to mark the wires and coil pack block if this makes it easier for you.
Now once your ready remove the HT lead connectors making it easier to get to the bolts. Some coil packs have 1 – 8 bolts/screws depending on the car. Make sure you get them all off before removing the coil pack you don’t want to break any screw housings, making it more difficult when putting a new coil pack on.
Installing Your Replacement Coil Pack
If you have replaced your spark plugs and leads make sure they have been done correctly and are ready to be used. Once your sure of this bolt your coil pack back on your car then re attach the leads to your coil pack in the correct order, as noted before. If you have forgotten the order check your car owners manual it will be in there.
Now once everything is correctly placed back together and it tidy. It is now time to start your engine. You should notice a smooth start and the engine should no longer idle. If you have starting problems check the car over again if there is no fault it may be your starter motor. You should notice a better fuel consumption rate and your car should run a lot smoother overall.
We hope you enjoyed our guide and have now successfully fixed a faulty coil pack, saving yourself a ton of money in the process!
Regards, The Beat The Mechanic Team