Description

Subaru IMPREZA, STI 2002 Service Manual

I have seen more than a few STi engines torn down with aftermarket manuals that skip the turbo-specific specs. You pull a head bolt to a generic value and then wonder why the head gasket weeps at 20 psi. That does not happen with this Subaru IMPREZA, STI 2002 Service Manual. It is the factory supplement written for the STi model—580 pages, published by Fuji Heavy Industries, with the exact torque sequences and diagnostic codes Subaru intended. If you are doing anything beyond an oil change on a 2002 WRX STi or Impreza turbo, you need this on your bench.

Engine Mechanical ME(STi) – What You Get

This section covers the turbo-specific mechanicals. Valve clearance adjustment, compression inspection, idle speed, ignition timing, and the full engine assembly removal and installation. The manual gives you the OEM tool list – for example, the preparation tools needed to lock the camshaft sprockets when removing the timing belt. Page 2 lists the general engine specifications including displacement and compression ratio. I have had junior techs skip the valve clearance step because the aftermarket book says “0.008 in” – but the STi gets a different spec. This manual calls out the exact clearance for both intake and exhaust Valve.

Variable Valve Timing Diagnostics – DTC Coverage

The AVCS system on the 2002 STi is picky. The manual includes a full list of diagnostic trouble codes (DTCs) for the Variable Valve Timing system: P0011, P0021, P0365, P0390, P1306–P1309. Each code has a dedicated diagnostic procedure with step-by-step wiring checks. You get the ECM I/O signal locations and electrical specifications. No guessing whether the solenoid is stuck or the camshaft position sensor is dead – the flow chart tells you exactly what to probe and at what voltage.

Specifications SPC – Dimensions, Capacity, Torque

You need the factory capacity data? Page 2 shows capacity for engine oil, transmission fluid, differential, coolant. But more importantly, the torque tables are there. I have seen stripped intercooler bolts because some guy used a generic 30 ft-lb. The STi intercooler water tank removal procedure is detailed – and the torque for that little bracket is in the specs. The suspension section covers alignment specs and steering gear torque. For the Brake system, pad thickness limits and caliper bolt torque are given. You can trust these numbers because they came from the Subaru engineering team, not a third-party compiler.

Emission Control and Pre-catalytic Converter

The STi uses a pre-catalytic converter mounted close to the turbo. The manual gives removal and installation steps for that component. Also covered: the tumble generator valve assembly and actuator. These are specific to the turbo engine and often misdiagnosed. If the check engine light comes on with a lean code and you see the tumble valves stuck, you need the factory removal sequence to avoid breaking the actuator bracket. The section also includes the exhaust temperature sensor – a common failure point on high-mileage STis.

Why This Manual Beats Any Aftermarket Reprint

Aftermarket manuals often reprint generic Impreza data and slap a “Turbo” sticker on it. This service manual is a supplement specifically for the STi model. The wiring diagrams in the Electrical section are STi-specific – different pinouts for the ECM and different grounds. The transmission section covers the 6-speed (STi) control systems. And the suspension data includes the inverted strut torque values. If you are restoring a 2002 STi or building a swapped car, using the correct factory document saves hours of cross-referencing. Compare it to earlier models like the SUBARU IMPREZA 1993 Service Manual – Section: Electrical Section; that one covers a different era. This one is the 2002 STi supplement.

Audience Fit – Who Needs This Manual

This is for the owner or shop that works on the 2002 Subaru IMPREZA WRX STi or the standard Impreza turbo. If you are doing a timing belt job, cylinder head overhaul, or chasing an intermittent misfire with stored DTCs, you will use the inspection procedures for Engine oil pressure, Fuel pressure, and Transmission drain plug torque. The beginner can follow the removal and installation steps as long as they have the listed preparation tools. The professional will appreciate the DTC diagnostic trees – no need to guess which sensor went bad.

Related Manuals

• Subaru Impreza Service Manual
• SUBARU Impreza 1994 Service Manual – Section: Engine Sction

For an external perspective on the evolution of Subaru diagnostics, you can refer to the Automotive Industry Overview. But remember: only factory Subaru documentation has the exact data for your STi.

FAQ

Does this manual cover the standard Impreza or only the STi?

It covers both, but the STi-specific data (6-speed, AVCS, intercooler water spray, inverted struts) is the focus. Standard Impreza sections are included only where they overlap.

What torque specs are listed for the cylinder head?

The manual does not list a generic value; it provides the STi specific bolt torque sequence and angle. You will find the exact numbers in the Mechanical ME(STi) section under Cylinder Head Assembly. The procedure includes the order of tightening and the final angle. Do not use a generic 22 ft-lb for the head bolts – the STi uses a torque-to-yield method with multiple stages. The manual also lists the required tool part numbers for the angle gauge. If you lose the sequence, you will warp the head – I have seen it happen.

Access the Factory Manual now to keep your 2002 STi running at peak performance. No guesswork, no aftermarket shortcuts – just the OEM data that Fuji Heavy Industries certified for this chassis.