Replacing a BMW 328i ignition coil is easier than you might think. Even if you aren’t the most technically adept person, this is a job that you can do at home with just a couple of simple tools and the replacement coils. Doing so will avoid the hassle of having your car parked away at a service center for a day or two and, more importantly, will save you the costs involved with having a technician do it.
We’ve put together a comprehensive guide on all you need to know about a BMW 328i ignition coil replacement, along with steps on how to change them.
What Causes BMW 328i Ignition Coil Failure?
The most common causes of ignition coil failure on the BMW 328i are heat, vibrations, moisture, oil leaks, or electrical problems. As the ignition coils are close to the engine, they are exposed to extreme heat and vibration. They’re designed to withstand these conditions, but like all things mechanical, they sometimes fail prematurely. You can learn more about this in our BMW ignition coil guide. Unfortunately, it’s not uncommon to see ignition coils fail on a 328i as early as 40,000 miles and sometimes even sooner.
Are Spark Plugs to Blame?
An ignition coil may also fail if the spark plug that it is connected to is worn out. In this case, the coil is forced to produce a higher voltage to fire a spark, and this can cause it to strain and eventually fail.
Other less common factors include moisture, oil leaks, and electrical problems like a blown fuse or faulty wiring.
Keep in mind that pushing your car’s performance constantly will notably reduce the lifespan of your coils. Similarly, if you’ve made performance updates to your 328i, you’re likely going to wear the coils out sooner, and you could find yourself having them replaced every 20,000-25,000 miles.
How Many Ignition Coils Does BMW 328i Need?
Most BMWs you’ll see on the road today, including the BMW 328i, use a coil-on-plug (COP) arrangement that employs one ignition coil for each cylinder. So, 328i cars from the E46 and E90 generation will feature six ignition coils, while the newer F30 328i uses only four coils since it is powered by an inline-four engine.
That said, the procedure to change them is essentially the same since the technology is similar.
Should You Change All Coils at Once?
Typically, ignition coils last for around 100,000 miles under normal usage and when the engine is maintained well. On most BMW 328i cars, this number is a lot lower, and many owners have reported failures as early as after 40,000 miles. If one of the coils on your BMW 328i fails even sooner, you may be able to get away with replacing just the defective one. An unusual failure like this might be from an underlying issue that’s affected only a particular 328i ignition coil. If this is the case, you’ll also save a little money as the other coils won’t have to be changed.
On the flip side, if all your coils have decent mileage on them, then a failure of one coil means that the rest are likely to follow suit soon. Since they’re all subject to the same working conditions, it’s unlikely that one of them has worn out sooner than the others. In this case, replacing all the coils at once will save you time and money.
Speaking of which, you might want to check the state of your spark plugs as well. Replacing the ignition coils is a good opportunity to swap out old spark plugs as well.
How to Replace Ignition Coils
Replacing the ignition coil on the BMW 328i is reasonably straightforward and doesn’t require a technical background. The steps involved are essentially the same regardless of which generation of the car you own.
Step 1 — Gain Access to The Engine
Gaining access to the ignition coils on the BMW E46 and the newer F30 328i is fairly simple. You only need to remove the engine cover, which you can do with the help of a socket wrench. The process is a little more comprehensive with the E90 generation. The last two coils, for the 5th and 6th cylinder, are covered by the engine acoustic cover on these cars.
To remove this cover, you need to start by removing the cabin air filter housing. Then, remove the plastic covers on either end of the housing — one of them is for a computer box, while the other covers the brake master cylinder. After this, unclip the wires that are attached to the cowling. This may be tricky as three hard-to-reach clips need to be detached.
Once the acoustic cover is removed, you’ll have complete access to the ignition coils.
Step 2 — Determine Which of Your 328i Ignition Coil Needs To Be Replaced
On newer BMWs, like the F30 328i, a failed ignition coil will light up the check engine light accompanied by an error code. Typically, the last digit of the code corresponds to which of your ignition coils has failed. However, if this isn’t the case, you’ll have to test the ignition coils manually to see which one is faulty. The simplest way to do this is to unplug the coils individually while the engine is running. When a good coil is unplugged, it will cause a change in the idling sound of your engine, while removing a faulty one won’t.
Another way of testing the coil is to figure out which cylinder is having issues, then moving that ignition coil to another cylinder. If the problem jumps along with the coil, you’ll know exactly what’s causing your issues.
Step 3 — Replacing The Coil
To remove an ignition coil, disconnect the wiring to the coil by unfastening the clip, firmly grip the coil and pull it out of its socket. You may have to twist them a little to get them out in some cases.
Once you’ve confirmed the faulty coil, you can replace it (or all the coils, if required) with a new one. Bosch ignition coils are some of the most popular choices for a replacement as they were factory-fitted for a lot of BMW 328i cars. The Bosch 0221504800 coil is a great OEM option.
Step 4 — Inspect All Coils
If you’re not replacing all the ignition coils, you can use the opportunity to check on the condition of the other coils plugged into the engine. You can do this with a multimeter; check the coil’s primary and secondary resistance — if either is out of the ordinary, it may be due for a replacement soon.
Also, check if the boots have any sort of imperfections. Even the tiniest of holes or tears can cause a grounding issue, which will render the coil ineffective.
Step 5 — Reassembly
The final step is to put everything back in order. Reconnect the coils to their respective wiring and reinstall the engine cover.
Use Quality Ignition Coils Only
It’s crucial that you replace a faulty ignition coil with one from a reliable OEM manufacturer. The most reputed names for the BMW 328i are Bosch, Eldor, and Delphi. These brands make trustworthy ignition coils, and your 328i already has a set from one of these names installed from the factory.
If you’re looking to replace your BMW 328i ignition coil, head over to our store and select your Bimmer using our car selection tool. Then, simply head over to the ignition section of the results, and you’ll find what you’re looking for.
