The Subaru EJ20 engine has earned a legendary status among car enthusiasts, known for its durability, versatility, and performance. Found in many Subaru models, including the Impreza WRX, this engine’s unique design and features make it stand out in the automotive world.
A critical aspect of its operation is its firing order, which plays a vital role in how the engine runs.
In this guide, we’ll explore the firing order of the Subaru EJ20 engine, explaining what it is, why it matters, and how it works. Whether you’re an experienced mechanic or just curious about your Subaru’s inner workings, this article will provide all the essential information.
Quick Navigation
Subaru EJ20 Firing Order
The firing order for the Subaru EJ20 engine is: 1-3-2-4
How the Firing Order Works
- Cylinder 1 Fires First: The ignition sequence begins with the front-right cylinder.
- Cylinder 3 Fires Next: The rear-right cylinder follows, alternating between banks.
- Cylinder 2 Fires Third: The ignition moves to the front-left cylinder.
- Cylinder 4 Fires Last: The sequence completes with the rear-left cylinder, then the cycle repeats.
Why Subaru Chose the 1-3-2-4 Firing Order
Subaru engineers carefully designed the 1-3-2-4 firing order for the EJ20 engine to optimize its unique boxer layout. Here’s why this firing order is ideal:
- Minimized Vibrations: Alternating between cylinders on opposite banks balances the engine and reduces vibrations.
- Smoother Power Delivery: The even distribution of power strokes ensures a smoother driving experience.
- Improved Efficiency: This firing order supports efficient airflow and combustion in the engine.
- Durability: Balanced operation extends the life of critical engine components.
What Is a Firing Order?
The firing order refers to the sequence in which the spark plugs ignite the air-fuel mixture inside the cylinders. This controlled ignition creates the power that drives the vehicle. In every engine, the firing order is carefully designed to ensure balance, efficiency, and smooth operation.
Why Does the Firing Order Matter?
- Smooth Performance: Proper sequencing minimizes vibrations and ensures consistent power delivery.
- Efficiency: Correct firing order optimizes fuel combustion, reducing waste.
- Engine Longevity: Balanced operation reduces stress on engine components.
- Power Output: Ensures the engine produces its maximum potential power.
Subaru EJ20 Engine Overview
The EJ20 is part of Subaru’s iconic EJ engine family, which includes several horizontally opposed (boxer) engines. The EJ20 specifically features a 2.0-liter displacement, making it a favorite for its balance of power and efficiency.
Engine Configuration
- Horizontally Opposed Design: The boxer engine layout features two banks of cylinders, with each pair of cylinders positioned opposite one another.
- Four Cylinders: Two cylinders per bank, giving the EJ20 its characteristic low center of gravity and smooth operation.
Cylinder Numbering
The cylinders in the EJ20 engine are numbered for reference:
- Cylinder 1: Front right (passenger side in left-hand-drive vehicles).
- Cylinder 2: Front left (driver’s side).
- Cylinder 3: Rear right (passenger side).
- Cylinder 4: Rear left (driver’s side).
How to Identify the Firing Order
Consult the Owner’s Manual
The owner’s manual provides detailed specifications about the engine, including its firing order and cylinder layout.
Look for Cylinder Markings
Cylinder numbers are often stamped on the engine block, near the spark plugs or injectors, for easy identification.
Use Service Manuals
Professional repair manuals include diagrams and step-by-step instructions that outline the engine’s firing sequence.
Common Issues Related to Firing Order
When the firing order is incorrect, it can disrupt the engine’s performance and lead to noticeable problems. Let’s look at the symptoms and causes of firing order issues.
Symptoms of Incorrect Firing Order
- Engine Misfire: Cylinders fail to ignite properly, causing uneven power output.
- Rough Idling: The engine vibrates excessively or feels unstable when idling.
- Loss of Power: The vehicle struggles to accelerate or maintain speed.
- Knocking or Pinging Sounds: Unusual noises can indicate irregular firing.
- Increased Fuel Consumption: Inefficient combustion leads to higher fuel usage.
Causes of Incorrect Firing Order
- Misconnected Spark Plug Wires: Spark plug wires may be improperly connected, disrupting the firing sequence.
- Faulty Ignition Components: Damaged spark plugs, ignition coils, or sensors can affect firing.
- Timing Issues: A misaligned timing belt or chain can throw off the ignition sequence.
Diagnosing and Fixing Firing Order Problems
If you suspect an issue with the firing order, follow these steps to diagnose and resolve the problem.
Diagnostic Steps
- Check Spark Plug Connections: Verify that the spark plug wires are connected to the correct cylinders according to the firing order.
- Inspect Ignition System: Examine the spark plugs, ignition coils, and wires for wear or damage.
- Verify Timing: Use a timing light to ensure the engine’s timing matches the manufacturer’s specifications.
- Scan for Error Codes: Use an OBD-II scanner to identify any misfire-related error codes.
Fixing Common Issues
- Rewire Spark Plug Connections: Ensure the spark plug wires follow the correct firing sequence.
- Replace Faulty Components: Replace damaged spark plugs, ignition coils, or sensors as needed.
- Adjust Timing: Align the timing belt or chain to restore proper synchronization.
Preventative Maintenance for Firing Order Reliability
Maintaining the correct firing order is critical for the EJ20’s performance and longevity. Here are some tips for ensuring firing order reliability:
Regular Inspections
- Check the condition of spark plugs, ignition coils, and wiring during routine maintenance.
- Look for signs of wear, corrosion, or loose connections.
Replace Components as Needed
- Replace spark plugs and ignition coils at Subaru’s recommended intervals to maintain consistent ignition.
Follow Subaru’s Maintenance Schedule
- Perform scheduled maintenance tasks, including timing belt or chain replacement, to prevent timing-related issues.
Use Quality Parts
- Always use OEM or high-quality aftermarket components to ensure compatibility and performance.
Engines with Similar Firing Orders
FAQs About Subaru EJ20 Firing Order
Can I Change the Firing Order?
No, the firing order is determined by the engine’s design and cannot be changed without significant modifications.
What Happens If the Firing Order Is Incorrect?
An incorrect firing order causes misfires, rough idling, power loss, and potential engine damage.
Is the Firing Order the Same for All Subaru Boxer Engines?
While many Subaru boxer engines share the 1-3-2-4 firing order, some variations may exist based on the specific engine model.
How Do I Verify the Firing Order?
Consult the owner’s manual or service manuals, and use cylinder markings or diagnostic tools to confirm the firing order.
Conclusion
The Subaru EJ20 engine’s 1-3-2-4 firing order is a crucial element of its design, ensuring smooth operation, balanced performance, and optimal efficiency. Understanding and maintaining this firing order is essential for anyone looking to keep their EJ20-powered Subaru running at its best.
By following proper maintenance practices, diagnosing issues early, and adhering to Subaru’s guidelines, you can enjoy reliable performance from this iconic engine for years to come. Whether you’re a seasoned mechanic or a Subaru enthusiast, appreciating the intricacies of the EJ20’s firing order is a step toward mastering the art of engine maintenance.
