🏷️ Basic Information

Make:

Subaru

Model:

Impreza WRX STI

Year:

2004

Chassis Code:

GDB-F

Generation:

GD

Generation Variant:

GD/GG (2nd Generation, 'F' model year update)

👋 Introduction

Vehicle Segment:

Compact Performance Sedan/Wagon (WRC Homologation Special)

Target Audience:

Enthusiasts, Owners Seeking In-depth Maintenance and Repair Information

Key Competitors 2004:

Mitsubishi Lancer Evolution VIII, Ford Focus RS, Honda Civic Type R (EP3), Volkswagen Golf GTI

Performance Focus:

Tuned turbocharged engine, Symmetrical All-Wheel Drive, Driver-focused chassis tuning

Rally Heritage:

Direct lineage from WRC success, providing rally-bred performance

Manual Value Proposition:

Enables owners to perform complex maintenance and repairs, enhancing vehicle longevity and performance potential.

📋 Manual Details

Main Coverage:

Complete Service and Repair Manual

Engine Coverage:

EJ257 Turbocharged Boxer Engine

Transmission Coverage:

6-speed Manual Transmission (TY856WR1JJ)

Chassis Coverage:

Suspension, Steering, Brakes, Drivetrain (AWD System)

Body Coverage:

Exterior and Interior Body Panels, Doors, Glass, Bumpers, Trim

Electrical Coverage:

Wiring Diagrams, Fuses, Relays, Lighting, ECUs, Sensors

Acoustics Coverage:

Noise, Vibration, and Harshness (NVH) Control

Estimated Pages:

Over 2000

Type:

Factory Service Manual (FSM) / Workshop Manual

Language:

English

Delivery Format:

Downloadable Digital File

Archival Format:

WinRAR Archive (.rar)

📖 Manual Coverage

Powertrain:

Engine, Fuel System, Ignition System, Exhaust System, Turbocharger System, Drivetrain, Transmission, Differentials (Front, Center, Rear)

Chassis And Suspension:

Front and Rear Suspension, Steering System, Brake System (ABS, Brake Booster, Master Cylinder, Calipers, Rotors, Lines), Wheel Hubs, Bearings

Body And Interior:

Body Panel Removal/Installation, Doors, Hood, Trunk, Seats, Interior Trim, Glass Replacement, HVAC System

Electrical And Electronics:

Engine Control Unit (ECU), Body Control Module (BCM), Powertrain Control Module (PCM), Wiring Diagrams, Fuses, Relays, Lighting Systems (Headlights, Taillights, Interior), Audio System, Power Accessories, SRS (Airbag) System

Diagnostics:

Troubleshooting Charts, Diagnostic Trouble Codes (DTCs), Symptom-based Diagnostics, Component Testing

Maintenance:

Scheduled Maintenance, Oil Changes, Filter Replacements, Fluid Checks and Replacements, Spark Plug Replacement, Belt Inspection and Replacement

Repair:

Engine Overhaul, Turbocharger Rebuild/Replacement, Transmission Overhaul/Replacement, Clutch Replacement, Brake Pad/Rotor Replacement, Suspension Component Replacement, Electrical Component Repair, Body Panel Repair

Installation:

Component Installation and Removal (e.g., Engine, Transmission, Turbocharger, Suspension Components, Body Panels)

Adjustment:

Valve Clearance Adjustment, Clutch Pedal Adjustment, Handbrake Adjustment

Depth Level:

Comprehensive (from basic checks to full engine/transmission rebuilds)

Diagnostic Capability:

Advanced Diagnostic Procedures, Component Resistance and Voltage Checks, Sensor Signal Analysis

Rebuild Specifications:

Detailed Torque Specifications, Clearances, Assembly Procedures for Major Components

📊 Manual Specifications

Digital Format:

PDF (likely extracted from original FSM)

Searchability:

Likely searchable text within PDF, depending on scan quality

Visual Quality:

Variable (dependent on original source scans/creation)

Binding:

N/A (Digital Download)

Paper Quality:

N/A (Digital Download)

⚙️ Engine Specifications

Engine Code:

EJ257

Engine Type:

Horizontally-Opposed (Boxer), 4-Cylinder, 16-Valve, DOHC, Turbocharged

Displacement:

2.5 Liters (2457 cc)

Bore X Stroke:

99.5 mm x 79.0 mm

Horsepower Usdm:

300 hp @ 6000 rpm

Torque Usdm:

300 lb-ft @ 4000 rpm

Compression Ratio:

8.2:1

Turbocharger Model:

IHI VF39

Intercooler Type:

Air-to-Air Top-Mount Intercooler

Fuel Delivery:

Sequential Multi-Port Fuel Injection (MPI)

Fuel Type:

Unleaded Premium Gasoline (91+ Octane Recommended)

Fuel Pump:

High-flow electric fuel pump

Engine Oil Capacity:

4.8 US quarts (4.5 liters) with filter change

Engine Oil Viscosity:

5W-30 (API SG or SH grade, or equivalent)

ECU Type:

Engine Control Unit (ECU) with specific STI calibration

🔧 Transmission

Type:

6-Speed Manual Transmission

Model Code:

TY856WR1JJ

Availability:

N/A (STI model exclusively 6MT)

Drivetrain Layout:

Symmetrical All-Wheel Drive (AWD) with Driver Controlled Center Differential (DCCD)

Front Differential:

Open Differential

Rear Differential:

Viscous Limited Slip Differential (VLSD)

Transmission Fluid Capacity:

2.2 US quarts (2.1 liters)

Transmission Fluid Type:

API GL-5, SAE 75W-90 Gear Oil (Subaru Extra-S recommended)

Type:

Hydraulically operated, single dry plate, diaphragm spring clutch

📐 Dimensions

Length:

173.8 inches (4415 mm)

Width:

69.7 inches (1770 mm)

Height:

57.7 inches (1465 mm)

Wheelbase:

104.7 inches (2659 mm)

Front Track:

59.8 inches (1519 mm)

Rear Track:

59.3 inches (1506 mm)

Curb Weight:

3285 lbs (1490 kg) approx.

Gross Vehicle Weight Rating:

4299 lbs (1950 kg)

Towing Capacity:

Not Recommended/Specified

Trunk Volume:

11.3 cubic feet (Sedan)

Standard Wheel Size:

17 x 7.5 inches

Standard Tire Size:

225/45R17

Bolt Pattern:

5 x 114.3 mm (5 x 4.5 inches)

Wheel Offset:

+53 mm

🛡️ Safety Features

NHTSA Frontal Driver:

5-Star (for 2004 model year Impreza)

NHTSA Frontal Passenger:

5-Star (for 2004 model year Impreza)

IIHS Moderate Overlap Frontal:

Good (for comparable 2nd Gen Impreza models)

ABS:

Standard Anti-lock Braking System (ABS)

E-Brake:

Rear Drum Parking Brake

Airbags:

Driver and Passenger Frontal Airbags, Side Airbags (optional on some trims)

Seatbelts:

3-point Front and Rear Seatbelts with pretensioners

Body Structure:

Ring-shaped reinforcement frame, reinforced passenger compartment

💡 Technology Features

Head Unit:

Factory AM/FM/CD player

Speakers:

Typically 6-speaker system

Traction Control:

No explicit Traction Control System (TCS) but AWD and DCCD provide significant traction benefits.

Cruise Control:

Standard electronic cruise control

Aux Input:

N/A (typically no standard auxiliary input)

Gauge Cluster:

Includes tachometer, speedometer, fuel gauge, coolant temperature, oil pressure warning light, DCCD indicator.

🔧 Maintenance

Oil Change Interval:

Every 3,750 miles or 3.75 months (severe driving) / 7,500 miles or 7.5 months (normal driving), based on Subaru recommendations and oil type.

Air Filter Replacement:

Every 15,000 miles or 15 months

Cabin Air Filter Replacement:

Every 15,000 miles or 15 months

Spark Plug Replacement:

Every 30,000 miles (NGK PFR7B or equivalent)

Timing Belt Replacement:

Not Applicable (EJ257 uses a timing chain)

Coolant Flush:

Every 30,000 miles or 30 months

Brake Fluid:

DOT 3 or DOT 4 (Subaru DOT3 recommended)

Power Steering Fluid:

Subaru ATF-HP or Dexron III equivalent

Coolant:

Subaru Super Coolant (Blue) or equivalent silicate-free, long-life coolant

Engine Failure Risk:

Piston ring land failure (ringland failure), connecting rod bearing wear, head gasket failure (less common on EJ257 than earlier EJ25s but still a concern).

Turbocharger Failures:

Bearing wear in VF39 turbo due to oil contamination or lack of lubrication.

Clutch Wear:

Early clutch wear or failure, especially with aggressive driving or modifications.

Susceptibility To Oil Sludge:

Requires diligent adherence to oil change intervals and using quality oil to prevent sludge buildup.

Differential Failure:

Potential for center and rear differential failure under extreme stress or poor maintenance.

📚 Vehicle History

Subaru Rally Success:

Dominant presence in World Rally Championship (WRC) with multiple manufacturer and driver titles, directly influencing STI models.

Impreza Development:

Introduced in 1992, the STI (Subaru Tecnica International) variants were developed for homologation and performance.

Gd Generation:

Second generation (GD/GG) launched in 2000, with significant updates in 2002 and 2004 (affecting bodywork, suspension, and engine management).

2004 Update:

Introduction of the 'F' model year for the GD chassis, featuring revised front-end styling (grille, headlights, bumper), wider track, and updated DCCD controls.

Manufacturing Location:

Ota City, Gunma Prefecture, Japan

Production Years Gdb:

2000-2007

🏆 Awards & Recognition

Sport Compact Car Achievement:

Often recognized by automotive publications like Sport Compact Car for performance and handling.

Car And Driver 10Best:

While not consistently on 10Best, the Impreza line often received nods for its performance and value.

Wrc Homologation:

STI models are WRC homologation specials, meeting FIA requirements for rally competition.