Is it hard to replace spark plugs on a Subaru?
Yes, it’s typically doable for a capable DIYer, but the level of difficulty varies by engine family and model year. Older EJ-series engines are generally easier to access, while newer FA/FB direct-injected and turbocharged engines can be more time-consuming and require more disassembly. Always check your specific engine code and the vehicle’s service manual for exact steps and torque specs.
In more detail, Subaru’s lineup has evolved through several engine generations, each with its own layout for spark plugs, ignition coils, and surrounding components. The overall task remains the same—remove old plugs, install new ones to specification, and reassemble—but the path to access can differ enough to affect how long the job takes and how challenging it feels for a home technician.
Engine architecture and plug access
Access to spark plugs in a Subaru varies with the engine family, ignition layout, and how much hardware sits around the plug wells. The general pattern is that older, naturally aspirated engines tend to be the easiest to service, while direct-injected and turbocharged engines add steps or require removing additional components.
- EJ-family engines (older Subaru 2.0L/2.5L): typically coil-on-plug arrangements with plugs accessible from the top of the engine bay, often straightforward for a DIYer.
- FA/FB engines (modern 2.0L/2.4L and related designs): direct injection and DOHC with plugs that sit deeper in the head or behind more surrounding hardware; access is more involved and may require removing intake components or related plumbing.
- Turbocharged variants: intercooler piping, intake ducts, and sometimes the turbo housing can add steps to reach the plugs, increasing time and complexity.
- Maintenance matters: some engines use longer-reach plugs or special gap specifications; others come pre-gapped but still require careful torque to avoid thread damage.
- Tools and space: limited clearance around the plug wells and the need for appropriate extensions, a torque wrench, and a spark plug socket are common across models.
In short, the simplest Subaru plug-change jobs are on older EJ-era engines, while the most involved tasks are seen on newer direct-injected or turbocharged designs. Always verify the exact engine code and consult your manual for model-specific guidance.
DIY readiness and steps
If you’re considering doing it yourself, here’s a practical guide to what to expect and how to approach the job safely and effectively.
- Confirm the exact engine code and the correct spark plug type and gap as specified by the factory service manual. Subarus use different plugs across engines, and mis-matched parts can cause misfires or damage.
- Disconnect the negative battery lead to reduce the risk of short circuits and to ensure proper coil removal without energizing the system unexpectedly.
- Remove any covers, hoses, or intake components that obstruct access to the plug wells (this is more common on FA/FB direct-injected or turbo models).
- If your engine uses a fuel rail that blocks access, carefully relieve fuel pressure and/or disconnect the rail as required by the service manual. Do not force components if you’re unsure.
- Disconnect ignition coils or coil packs and note their positions for correct reinstallation. Lift the coils straight up to avoid damaging the connectors.
- Carefully clean around each plug well to prevent debris from falling into the cylinder. Remove the old plugs with a properly sized spark plug socket and extension, then keep debris away from the openings.
- Thread the new plugs in by hand to ensure clean engagement and avoid cross-threading, then torque to the manufacturer’s specification with a calibrated torque wrench.
- Reconnect the ignition coils, reinstall any removed components, and reconnect the battery. Start the engine and listen for smooth running; a misfire or rough idle may indicate a misinstalled plug or an ignition issue.
- Dispose of used plugs properly and reset maintenance reminders if applicable.
Turbo and direct-injected engines, plus vehicles with tighter engine bays, can require more careful disassembly and longer job time. If you’re unsure about depressurizing the fuel system, torque specs, or coil reassembly, consider professional service to avoid potential damage.
Summary
Spark plug replacement on a Subaru is not uniformly hard. It’s typically within reach for a capable DIYer on older, naturally aspirated engines, but newer direct-injected and turbocharged models present additional access challenges that can extend the job. Always verify the exact engine code, consult the service manual for steps and torque specifications, and seek professional help if the layout or required disassembly seems beyond your comfort level.
