Over its decade-long production run from 2006 to 2016, the BMW N54 engine powered multiple Bimmer models, including the E90 3-Series, E60 5-Series, and the E89 Z4. The 3.0L inline-six unit was the German marquee’s first mass-produced turbocharged gas engine and was met with much criticism.
However, the N54 also had its fair share of troubles. Apart from the infamous High-Pressure Fuel Pump (HPFP) failures that culminated in a class action lawsuit, there were a couple of other issues that several owners reported. One of them was excessive carbon deposits in the engine. The N54 carbon build-up issue is something that multiple owners have had to deal with, and you’ll find numerous posts on forums with people asking for help.
If you’re the owner of an N54-powered car, there are some steps you can take to delay or reduce the effects of carbon build-up in your engine. This article will tell you all you need to know about the N54 carbon build-up issue, with what you can do to rectify the problem if your engine has already been affected.
What Causes Carbon Build-Up in an Engine?
Every internal combustion engine burns a mixture of fuel and oxygen to produce power. This reaction results in multiple products usually eliminated by the exhaust system. Improper or inefficient combustion within the cylinders can result in carbon deposits within the engine, usually in the form of a thick, black tar-like substance. As you can imagine, accumulating these carbon deposits inside the engine can result in several issues.
The N54 carbon build-up is most common in the intake ports of the cylinder head and is most often caused by the direct injection system in the car. When there’s a mismatch between the intake valve and fuel injection timing, it can cause carbon build-up within the engine. Other factors contributing to carbon build-up include excessive idling, low-quality fuel, and poor engine maintenance.
What Are Signs of Carbon Build-Up in an Engine?
Carbon build-up in engines is a serious issue that can cause much damage if left unchecked. Several signs indicate carbon build-up, and it’s essential to be aware of them, so you can take steps to fix the problem before it becomes too severe.
One of the most common signs of carbon build-up is decreased engine performance. If your engine starts to feel sluggish or doesn’t have the same power as it used to, it could be a sign of too much carbon build-up on the valves. This can also lead to increased fuel consumption and emissions, so it’s definitely something you want to take care of right away.
Another sign of carbon build-up is engine misfires. Carbon build-up can prevent proper combustion, which leads to engine misfires. If your engine starts to misfire, it could also mean there’s an issue with the spark plugs or other ignition system components.
If you notice any of these signs, taking action immediately is crucial. The longer you wait, the more damage carbon build-up can do to your engine.
How Do You Prevent N54 Carbon Build-Up?
If you’ve recently serviced your engine, or if you’ve determined that the valves in your engine aren’t suffering from carbon build-up, there are some measures you can take to prevent it from happening again. To check the conditions of your valves, you will need to remove the intake manifold and visually inspect the intake valves on your engine. If you see thick, black soot around the valves, it’s time to have them cleaned.
One of the most straightforward ways to avoid N54 carbon build-up is to stay on top of basic engine maintenance. This includes timely spark plug replacement and regular oil changes. Since the issue on the BMW N54 engine is caused by the fuel injection system, it’s also a good idea to ensure that the fuel pump and injectors are also in excellent health and replaced when required.
If you’d like to go the extra mile, BMW sells fuel additives designed to clean the fuel system and reduce the probability of excessive carbon build-up. Some owners also recommend taking your car out on the highway and keeping the engine in the mid-range of the rev band. Theoretically, this slightly stressed and higher-temperature engine state should cause some of the carbon in the engine to be burnt away.
That said, there isn’t a product out there that can beat the effectiveness of diligent engine maintenance.
How Do You Fix N54 Carbon Build-Up?
If you’ve just bought a pre-owned E90 3-Series, or another car powered by the N54 engine and find that its engine already has excessive carbon around the valves, your only course of action is to have it cleaned. The simpler but more expensive method would be to hand it over to a technician and have them do all the dirty work.
On the other hand, if you have some time and the right tools, cleaning the N54 carbon build-up is something you can carry out yourself. Broadly speaking, there are two methods to doing so — walnut blasting and manually cleaning the valves. While the former is a more straightforward, less time-consuming affair, the latter is more affordable.
We’ll dive into what each method entails further below, so you can decide what’s best for you. The initial steps for carrying out either process are identical.
- Remove the engine cover
- Disconnect the spark plugs, the piping that connects the intake manifold to the intercooler, and the piping to the turbocharger.
- Since the N54 is an inline-six engine, you should find that two of the intake valves are in the open position while four of them are closed. If you can’t visually confirm that the valves are open or closed, an easy method is to spray some WD-40 into the intake holes and see if it accumulates — if it does, the valve is closed.
- The two open valves will need to be blocked. You can use automotive masking tape or seal it with a microfiber cloth to ensure that your cleaning fluid or walnut shells don’t enter the engine.
- Once the closed intake valves have been cleaned, you will have to rotate the crankshaft, so the two open valves are now closed and can be cleaned. You can do so by manually turning the crank pulley or disconnecting the fuel pump from the engine and cranking it over for a second. Either way, always check that the valves are fully closed before you start cleaning anything.
Manual Cleaning
Manually cleaning the intake valves will require purchasing an engine cleaning brush kit and some valve cleaning fluid, which should amount to less than $50. Follow the above steps to ensure that four N54 engine valves are closed, and fill these valve holes with the cleaning fluid. Let it sit for a few minutes. The cleaning fluid will break down the carbon build-up in the engine to a more liquid state that’s easier to remove and deal with.
After the fluid has been sitting in the valve holes for a bit, take the cleaning brushes and scrape off as much carbon deposit as possible. Then use a microfiber cloth to soak the fluid and remove it. Finally, any remaining carbon close to the valves can be removed using compressed air.
Walnut Blasting
Walnut blasting your engine is similar to the sandblasting that a technician will perform. It involves forcefully firing walnut shells into the closed intake valves and cleaning up the gunk. You will need a walnut blaster to accomplish this, so it requires a hefty investment upfront and doesn’t make a lot of sense if you’re performing this only on your car.
It is quicker than manually cleaning the valves, so it might make sense if you’re short on time and willing to spend the money. We’d also recommend using a vacuum cleaner alongside the walnut blaster to significantly reduce the amount of walnut shell dust in the intake walls and around your engine bay and workspace.
Get Only Genuine Spares for Your BMW N54 Engine
As mentioned above, it’s impossible to avoid carbon build-up in this type of direct injection engines. However, with timely maintenance and proper care, you can delay the inevitable and reduce the damage caused to your engine.
To get genuine BMW and aftermarket spares, enter the model and year of your vehicle in the shop section of Bimmers.com. We’ll only show you high quality parts that perfectly match your BMW.
