Vehicle Segment:
Performance Compact Sedan/Wagon, Rally-bred Sports Car.
Key Competitors:
Mitsubishi Lancer Evolution, Ford Focus RS, Honda Civic Type R (in broader performance segments).
Vehicle Highlights:
Iconic turbocharged boxer engine, advanced Symmetrical All-Wheel Drive, performance-tuned suspension, DCCD, potent braking system, rally heritage.
Diy Enablement:
Empowers owners to perform a wide range of repairs and maintenance, saving on labor costs and fostering a deeper understanding of their vehicle.
General Coverage:
Comprehensive repair and maintenance for the Subaru Impreza WRX STI.
Specific Systems:
Engine, Drivetrain, Suspension, Steering, Brakes, Electrical System, HVAC, Bodywork, Emissions.
Estimated Page Count:
Approximately 2000+ pages (typical for comprehensive factory service manuals of this era).
Manual Type:
Factory Service Manual (FSM) / Repair Manual
Engine Management:
Detailed diagnostics and repair procedures for the EJ257 engine, including ECU functions, sensors, actuators, and fuel injection systems.
Drivetrain And AWD:
In-depth coverage of the symmetrical All-Wheel Drive system, including DCCD (Driver Controlled Center Differential), viscous coupling unit, front/rear differentials, and gearbox maintenance/overhaul.
Suspension And Steering:
Complete information on the performance-tuned suspension, including strut assembly removal/installation, alignment procedures, power steering system diagnostics, and steering rack overhaul.
Braking System:
Detailed procedures for the performance Brembo braking system, including rotor and pad replacement, caliper servicing, brake fluid bleeding, and ABS system diagnostics.
Electrical System:
Comprehensive wiring diagrams, troubleshooting guides for lighting, starting/charging systems, infotainment, and various control modules.
Routine Maintenance:
Oil changes, filter replacements (oil, air, fuel), coolant flush, spark plug replacement, belt inspection and replacement.
Engine Repair:
Top-end rebuilds (cylinder heads), bottom-end overhauls, turbocharger diagnostics and replacement, intercooler system servicing.
Transmission Overhaul:
Detailed steps for clutch replacement, gearbox disassembly and reassembly, transfer case servicing, and differential rebuilds.
Troubleshooting Diagnostics:
Systematic diagnostic trees and fault code interpretation for common and complex issues.
Depth Of Coverage:
Covers everything from basic fluid checks and filter changes to complete engine and transmission rebuilds, including component-level diagnostics and specifications.
Searchability:
Searchable text for quick information retrieval.
Printability:
High-resolution, optimized for clear printing of text and diagrams.
Zoom Capability:
Excellent zoom capability for detailed inspection of diagrams and text.
Binding Description:
N/A (Digital PDF format)
Paper Description:
N/A (Digital PDF format)
Operating Systems:
Compatible with all Windows and macOS operating systems.
Engine Type:
2.5L DOHC turbocharged flat-four boxer engine
Horsepower Output:
300 hp @ 6000 rpm (approx.)
Torque Output:
300 lb-ft @ 4000 rpm (approx.)
Fuel Delivery:
Multi-point fuel injection (MPI) with top-feed injectors.
Recommended Fuel:
Premium Unleaded Gasoline (91 octane or higher)
Coolant Type:
Subaru Super Coolant (Blue) or equivalent silicate-free OAT coolant.
Oil Type:
Synthetic SAE 0W-30 or 5W-30
Oil Capacity:
4.8 US quarts (4.5 Liters) with filter
Turbo Model:
IHI VF39 (typical for this generation)
Transmission Type:
6-speed Manual Transmission
Optional Transmission:
N/A (STI models were exclusively manual)
Dccd System:
Driver Controlled Center Differential (DCCD) for adjustable torque split.
Transmission Fluid Type:
Subaru Extra Synchros 75W-90 GL-5 (gearbox) / Subaru Extra Synchros 75W-90 GL-5 (transfer/rear diff, though separate fill often specified).
Clutch Fluid:
DOT 3 or DOT 4 brake fluid
NHTSA Front Impact Rating:
4/5 Stars (for comparable 2004 Impreza models, STI specific may vary slightly)
IIHS Side Impact Rating:
Good (for comparable 2004 Impreza models)
ABS:
Standard Anti-lock Braking System (ABS)
Traction Control:
Standard Traction Control System (TCS) and Vehicle Dynamics Control (VDC).
Airbags:
Front airbags, side airbags, and curtain airbags (depending on specific market/trim).
Seat Belts:
3-point seatbelts with pretensioners and force limiters.
Body Structure:
Reinforced unibody construction with crumple zones.
Audio System:
Factory AM/FM/CD player with optional premium audio.
Display System:
Basic digital/analog instrumentation, no advanced touchscreen infotainment.
Cruise Control:
Standard electronic cruise control.
Usb Aux Input:
Generally not equipped with factory USB/Aux inputs; aftermarket solutions common.
Oil Change Interval:
Every 3,000-5,000 miles or 3-6 months, especially under spirited driving conditions.
Spark Plug Replacement:
Approximately every 60,000 miles (refer to manual for specific type and gap).
Timing Belt Replacement:
Approximately every 105,000 miles or 7 years (critical maintenance item for EJ engines).
Brake Fluid Type:
DOT 3 or DOT 4
Power Steering Fluid:
Subaru Genuine Power Steering Fluid or Dexron III/Mercon compatible ATF.
Coolant Capacity:
Approx. 7.1 US quarts (6.7 Liters)
Piston Ring Land Failure:
Common issue in early EJ257 engines, particularly with aggressive tuning or poor maintenance. Manual provides diagnostics and repair procedures.
Turbo Seal Wear:
Turbocharger seals can wear, leading to oil consumption. Manual covers inspection and replacement.
Clutch Wear:
High-performance driving can accelerate clutch wear. Manual provides replacement procedures.
Suspension Component Wear:
Bushings and bearings can wear over time, affecting handling. Manual details replacement.
Rally Connection:
Subaru's deep roots in the World Rally Championship (WRC), directly influencing the Impreza WRX STI's development and reputation.
Gc8 To Gd Transition:
This generation (GD chassis) marked a significant design and engineering evolution from the previous GC8 generation.
Sti Distinction:
The STI variant represents the pinnacle of the Impreza line, featuring a more powerful engine, upgraded drivetrain, and enhanced chassis components compared to the standard WRX.
Manufacturing Location:
Japan (Subaru's primary manufacturing base)
Car And Driver 10Best:
While the STI itself might not have been on the 10Best list, the Impreza platform often featured highly in performance car discussions and comparisons.
Rally Championships:
Numerous WRC titles and championships secured by Subaru factory rally cars, directly validating the Impreza platform's performance capabilities.
Performance Car Status:
Consistently recognized as a benchmark for affordable, high-performance all-wheel-drive sports sedans.
