Subaru FA20 Engine Problems
The 2.0 Subaru FA20 engine was introduced in 2012 in two variants. The FA20D engines are non-turbo and use direct and port injection. The FA20F, on the other hand, features a twin-scroll turbocharger and direct injection. Both variants of the Subaru FA20 were named to Wards Auto’s list of the ten best engines.
They’re excellent engines that strike an excellent balance between performance and efficiency. However, perfect engines do not exist, and this is not an exception. We will discuss common problems with the Subaru FA20 engines in this article and conclude with some general thoughts on reliability.
FA20 Engine Specs & Info
The following are some of the basic specifications for the FA20D and FA20F engines. Nota bene – the Subaru FA20F is also known as the FA20DIT, with the DIT abbreviation standing for “direction injection turbocharged.”
|Aspiration||Naturally Aspirated||Twin Scroll Turbo|
|Fuel Injection||Port & Direct||Direct|
|Horsepower||197-205 HP||250-296 HP|
|Torque||151-156 lb/ft||258-295 lb/ft|
|Bore x Stroke||86 mm x 86 mm||86mm x 86mm|
|Compression Ratio||12.5 : 1||10.6 : 1|
As previously stated, the specifications of the two engines are comparable. After all, both engines are FA20s. The FA20D is a non-turbocharged engine with port and direct fuel injection.
Meanwhile, the Subaru FA20DIT gains a twin scroll turbocharger but loses its port injection. To accommodate the increased power and boost, the turbo variant’s compression ratio is reduced from 12.5 to 10.6. Otherwise, the Subaru FA20’s basic design is nearly identical.
- 2012-2020 Subaru BRZ
- 2012-2020 Toyota GT86
- Scion FR-S
- 2012+ Subaru Legacy 2.0GT
- 2014+ Subaru Leborg
- 2015+ Subaru WRX
- 2014-2018 Subaru Forester
4 Common FA20 Engine Problems
Several of the most frequently encountered problems with the Subaru FA20 engine include the following:
- Carbon build-up
- Connecting rods
- Factory tune
- Valve springs
We’ll discuss these issues in greater detail throughout the remainder of this article. However, now is an excellent time to add a few notes before proceeding. These are the most frequently encountered problems with the Subaru engine. That is not to say they are widespread or affect a sizable proportion of automobiles.
Additionally, the majority of the issues we’re discussing pertain to the FA20DIT turbo engine. Where necessary, we will make a distinction between the engines. With that in mind, let us discuss each of the aforementioned FA20 engine issues.
1) Subaru FA20 Carbon Build-Up
We frequently write about carbon build-up on a variety of newer engines. Direct injection (DI) is an excellent technology that contributes to the FA20 engine’s increased performance and efficiency.
However, DI has a few drawbacks of its own, the primary one being carbon build-up. To emphasize, carbon build-up is not an issue with the FA20D due to its port and direct injection configuration.
Why is this issue unique to the Subaru FA20DIT? Direct injection delivers all fuel directly into the cylinders. Naturally, engines generate some oil blow-by that travels through the intake tract.
Eventually, oil blow by finds its way onto the intake ports and valves, where it begins to form carbon deposits. With port injection, fuel is sprayed into this area, washing away any oil deposits.
Once an excessive amount of carbon is accumulated, the cylinders no longer receive optimal air flow. This is because the deposits gradually reduce the size of the intake ports, which can result in drivability issues.
Carbon build-up on the Subaru FA20 should become an issue between 60,000 and 100,000 miles. It is not a critical issue that requires immediate attention.
FA20DIT Carbon Build-up Symptoms
Excessive carbon build-up on the FA20 turbo direct injection engine manifests itself in the following ways:
- Rough idle
- Power loss
Typically, misfires are the precursor to problems with carbon deposits on the intake valves. Additionally, you’ll probably notice rough idle and stuttering or hesitation while accelerating. Due to the decreased airflow to the cylinders, the FA20 will also lose power. However, this symptom is typically difficult to detect because carbon build-up occurs gradually.
Subaru FA20 Carbon Deposits Fix
Generally, walnut blasting is the most effective method of removing carbon deposits. Naturally, the intake manifold must be removed in order to gain access to the intake ports and valves. The carbon deposits are then removed using a shop vac and walnut media shells.
Because the supplies required for the job are relatively inexpensive, the fix is primarily labor-intensive. Walnut blasting the FA20DIT intake valves will cost approximately $400-600+. Again, this is not an emergency repair, but it is prudent maintenance to perform every 60,000 to 100,000 miles.
2) FA20 Connecting Rod Engine Problems
This may not be an appropriate item to include on a list of common FA20 engine failures. However, it’s worth noting because the turbo engine is extremely easy to tune and modify. On stock FA20 engines, connecting rods are not a significant issue. They could still fail, but it is highly improbable. Increase the boost and torque, and the story changes.
FA20F connecting rods have been known to fail around the 325-350 lb-ft torque range. It’s not difficult to get the Subaru FA20 turbo engine into that range with a tune and mods. Again, this is not a significant concern at current levels of stock power.
Nonetheless, it’s worth mentioning because connecting rod failures are a serious problem. If a rod is bent and the engine begins to knock, a rebuild of the FA20 engine is required. In the worst-case scenario, you may require a completely new engine.
While this is not the type of failure you want to encounter, if you intend to modify the FA20, you should be aware of the possibility. We’ll skip over discussing connecting rod symptoms and solutions. Rather than that, the following section will discuss several risk mitigation strategies.
Reducing Risk of Subaru FA20 Rod Failure
Several methods exist for minimizing the risk of connecting rod problems on the FA20DIT engine, including the following:
- Keep boost under 22psi
- Limit low-end torque
- Conservative tuning
The first three points are mutually exclusive. Maintain a conservative tuning strategy for the FA20 engine. Maintain a boost pressure of 21-22psi and be cautious of low-end torque. At lower RPMs, the pistons move more slowly.
This exposes the engine to elevated pressures for an extended period of time, increasing the possibility of pre-detonation. Typically, it is pre-detonation that bends rods on the FA20DIT, especially near the safe limits.
Otherwise, keep a frequent data log. Keep an eye on fueling, AFRs, and ignition timing, among other things. If you notice an excessive number of timing pulls, you should consider adjusting the tune to remove some timing.
Because lean AFR’s are dangerous, this is another critical data point to monitor. We’ll write some tuning and modification guides for the FA20 engine in the future and delve deeper into these topics.
3) Subaru FA20 Factory Tune Issues
We’re going to move quickly through this discussion. Certain FA20DIT owners are dissatisfied with the factory engine software (“tune”) included with the car.
According to some reports, it’s quite aggressive when boosted, lacks smoothness, and runs too lean. Appropriate software for an engine requires a great deal of effort and knowledge. Additionally, individuals have varying methods for tuning and setting up engines.
Additionally, there may be some misunderstandings. As a direct injection engine, the Subaru FA20 is able to run slightly leaner than traditional port injection engines. People used to complain that the stock BMW N54 tune was far too lean. In reality, the majority of them were simply unfamiliar with the nature of DI.
The point is that we do not entirely believe the criticisms leveled against the factory software on the FA20 engines. The majority of owners will likely be unaware of any issues. Additionally, it’s simple to work with a tuner and fine-tune the instrument to your specifications. As such, we do not believe this is a genuine issue with the FA20.
4) FA20D Valve Spring Failures
Acceptable – we’ll keep this brief as well. We make an effort not to include recall-related topics in any common problem posts, as these are issues that the manufacturer is aware of and working to resolve.
The FA20D valve spring issues, on the other hand, are an intriguing subject. We’re specifying the naturally aspirated engine here because there is no known significant issue with the FA20DIT turbo motor.
In any case, Subaru and Toyota have issued a recall for valve springs in the Subaru BRZ, Toyota 86, and Scion FR-S equipped with the FA20D engine.
Excellent – they identified a defect and attempted to assist owners through a lengthy and costly recall. The job requires disassembly of the engine in order to access the valve springs and requires more than ten hours of labor.
However, some owners have reported additional issues following the valve spring repair. The technicians working on the recalls may be applying an excessive amount of sealant, which then mixes with the engine oil.
It eventually resulted in a few complete engine failures. It appears to be primarily affecting the FA20 engine found in the Toyota 86. We’ll leave it at that, as this is a highly debated subject with a lot of information floating around.
Subaru FA20 Reliability
How reliable are the Subaru FA20 and FA20DIT engines? We’ll rate the Subaru FA20’s reliability as average. It may even earn more than the average, but there are still some uncertainties.
The NA Subaru FA20D engine is relatively free of common problems. However, there is the valve spring recall nightmare, but it’s difficult to fault the company too much. Engines that are newly released will always have a few kinks to work out.
On the other hand, the FA20DIT has a few more widespread issues. This makes sense, as turbo engines are more complex and have a greater number of moving parts. Subaru’s decision to eliminate port injection is odd, given that DI causes carbon build-up issues on the FA20.
Otherwise, keep an eye out for connecting rod failures at higher than stock power and torque. While the FA20DIT is simple to tune and modify, this can cause the rods to approach their safe upper limits.
Having said that, the FA20 engines are solid in general, offering an excellent balance of reliability, performance, and efficiency. Maintain them properly, and you’re likely to have a positive experience for many years.
What are your thoughts on the Subaru FA20 engine?