A Guide to Replacing Fuel Injectors on the 2015-2018 Subaru WRX
Keep your FA20DIT engine running strong by understanding fuel injector failure and replacement.
- Choose an OEM-equivalent brand like Hitachi for guaranteed fit and performance.
- Always replace all four injectors as a set to comply with a Subaru TSB and ensure balanced engine operation.
- Symptoms like misfires may be caused by carbon buildup, a common issue on the FA20DIT engine that should be ruled out first.
- A fuel smell is a critical symptom of a leak and should be addressed immediately.
Is Your WRX's Fuel Injector Failing?
A bad fuel injector in your WRX can cause noticeable engine problems. Because the FA20DIT engine is sensitive to fuel delivery, a faulty injector can disrupt the air-fuel balance and cause issues ranging from annoying to serious. Watch for a combination of these signs.
Common Symptoms of a Bad Injector:
- Rough Idle: The engine may shake or vibrate more than usual when stopped.
- Engine Misfires: You might feel the engine hesitate or stumble, especially during acceleration. This can feel like a vibration or shudder. A check engine light with codes from P0300 to P0304 often points to a misfire.
- Poor Fuel Economy: If an injector is stuck open or closed, your fuel mileage may drop noticeably.
- Check Engine Light: Besides misfire codes, you might see codes related to the injector circuit (like P0200-P0204) or fuel pressure (like P0087).
- Fuel Smell: A strong smell of gasoline in or around the car could mean an injector is leaking.
A Note on Carbon Buildup
The FA20DIT engine is known for carbon buildup on the intake valves, typically every 60,000 to 100,000 miles. This happens because direct injection doesn't wash the valves with fuel. Symptoms of carbon buildup—like misfires, rough idle, and power loss—are nearly identical to failing fuel injectors. Subaru has issued a Technical Service Bulletin (TSB 09-74-21R) with a procedure for cleaning these deposits. Before replacing injectors for a misfire, consider a carbon cleaning service (walnut blasting) first, as this may be the real cause of your problem.
Choosing the Right Aftermarket Fuel Injector
When replacing a fuel injector, you want a part that performs just like the original. For your WRX, the choice between available aftermarket brands is straightforward.
Brand Quality Tiers
- OEM-Equivalent (Hitachi): Hitachi is a well-known original equipment manufacturer for many Japanese auto brands, including Subaru. Choosing a Hitachi-branded injector often means you are getting the exact same part that Subaru sells at the dealership, just in a different box and at a better price. For reliability and performance, this is the recommended choice.
- Standard Aftermarket (Standard Ignition): Standard Ignition is a reputable aftermarket brand that produces a wide range of replacement parts. While a viable option, Hitachi's status as an original equipment supplier makes it a more proven choice for this specific engine.
Replace as a Set
It is highly recommended to replace all four fuel injectors at the same time. Subaru issued a TSB (09-65-16) for 2015-2017 models announcing an updated injector design to prevent water intrusion. The bulletin specifies that if any injector is replaced, all four must be updated to the new part number to ensure proper function and sealing. Replacing them all at once ensures they are flow-matched, promoting a smoother, more balanced engine operation.
Cost of Replacing a 2015-2018 Subaru WRX Fuel Injector
The cost will depend on the parts you choose and whether you do the work yourself or hire a professional.
| Part or Service | Estimated Cost |
|---|---|
| New OEM Injector (Single) | $240 - $270 |
| New Aftermarket Injector (Single) | $144 - $179 |
| Shop Labor (Full Set Replacement) | $400 - $700 |
| Total Professional Job (Full Set, Aftermarket) | $976 - $1416 |
Cost estimates are based on national averages and may vary by location and supplier. Labor costs are for replacing all four injectors, which is the recommended procedure.
Frequently Asked Questions
Do I have to replace all four fuel injectors at once?
Yes, it is strongly recommended. Due to a design update detailed in Subaru TSB 09-65-16, all four injectors should be replaced with the new, improved part to ensure compatibility and prevent issues. This also guarantees that all injectors have the same fuel flow rate, which is crucial for engine smoothness and performance.
Is it hard to replace WRX fuel injectors myself?
It is a moderately difficult job. The injectors are located under the intake manifold, which must be removed for access. You also need to safely depressurize the high-pressure fuel system before starting. While possible for an experienced DIY mechanic, it is more complex than many other repairs.
Will a new fuel injector fix my engine misfire?
It might, but it's not guaranteed. Misfires in the FA20DIT engine can be caused by a bad injector, a faulty ignition coil, a bad spark plug, or carbon buildup on the intake valves. It's important to diagnose the problem correctly. Many shops will recommend a carbon cleaning service before replacing injectors to rule out that common issue.
Are there any recalls for the 2015-2018 WRX fuel injectors?
No, there are no specific safety recalls for the fuel injectors on this vehicle. However, Subaru did issue several Technical Service Bulletins (TSBs) related to injector design changes and cleaning procedures to address performance issues like misfiring.
Helpful Videos
Technical Specifications
OEM Part Numbers: 16600AA300 16637AA030
High-Pressure Direct Fuel Injector for FA20DIT Engine
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The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
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