🏷️ Basic Information

Make:

Porsche

Model:

928 S

Model Year:

1988

Body Style:

2+2 Coupe

Internal Model Code:

928

👋 Introduction

Positioning:

The Porsche 928 was positioned as a luxury grand tourer, a departure from Porsche's traditional sports car heritage. It was designed to compete with European and American luxury coupes.

Competitors:

Competed with models like the Jaguar XJ-S, BMW 6 Series, Mercedes-Benz SLC/SL.

Powertrain Layout:

Front-engine, rear-wheel drive.

Design Philosophy:

Transaxle design for weight distribution, powerful V8 engine, high level of comfort and technology for its era.

Value Proposition:

Empowers owners and independent mechanics to diagnose and resolve complex electrical issues, potentially saving significant dealership service costs. Crucial for maintaining the sophisticated systems of the 928.

Target Audience:

Porsche 928 owners, independent Porsche specialists, classic car repair shops.

📋 Manual Details

Primary Focus:

Electrical System Troubleshooting and Repair

Additional Coverage:

Wiring Diagrams, Component Identification, Electrical Fault Diagnosis

Estimated Page Count:

Varies by specific print run, but typically 100+ pages for a dedicated wiring diagram manual.

Type:

Wiring Diagram Manual / Electrical Troubleshooting Manual

Language:

English

Format:

Likely printed manual, potentially available in PDF format for digital distribution.

📖 Manual Coverage

Engine Management Electronics:

Ignition, Fuel Injection (L-Jetronic/KE-Jetronic variants), Engine Control Unit (ECU) related wiring.

Lighting System:

Headlights, taillights, interior lighting, auxiliary lighting.

Instrumentation And Gauges:

Speedometer, tachometer, fuel gauge, oil pressure, temperature, warning lights.

Comfort And Convenience:

Power windows, power locks, power seats, climate control system, central locking, sunroof operation.

Audio And Communications:

Factory radio/cassette system wiring, speaker wiring, antenna system.

Safety Systems:

ABS (Anti-lock Braking System) wiring, basic airbag system wiring (if applicable to '88 model).

Charging System:

Alternator, voltage regulator, battery wiring.

Starting System:

Starter motor, ignition switch, starter solenoid wiring.

Wiper And Washer System:

Wiper motor, washer pump, switch wiring.

Troubleshooting Methodology:

Step-by-step diagnostic procedures based on symptoms, often utilizing a process of elimination.

Component Testing:

Guidance on how to test individual electrical components (e.g., relays, solenoids, sensors) for proper function.

Wiring Harness Tracing:

Detailed diagrams showing the routing and connections of various wiring harnesses throughout the vehicle.

Fuse And Relay Identification:

Location and function of all fuses and relays, with diagrams indicating their specific circuits.

Connector Pinouts:

Detailed diagrams showing the pin configurations of various electrical connectors.

Depth:

Comprehensive, targeting professional technicians and knowledgeable DIY enthusiasts. Assumes basic understanding of automotive electrical principles and use of diagnostic tools (multimeter, test lights).

Diagnostic Focus:

Primary focus on diagnosing electrical faults and guiding repair actions.

📊 Manual Specifications

Digital Format:

PDF (if available digitally) with searchable text and high-resolution diagrams.

Print Quality:

High quality, often on durable paper suitable for workshop environments. Diagrams are typically crisp and clear.

Binding:

Typically perfect bound or spiral bound for ease of use and lay-flat functionality.

Paper Type:

Durable paper stock, often with a semi-gloss finish to protect against workshop grime.

⚙️ Engine Specifications

Engine Type:

V8

Displacement:

4.7 Liters (for early models), 5.0 Liters for later S models. The '88 S model typically features the 5.0L.

Bore X Stroke:

Approximately 97.0 mm x 84.0 mm (5.0L variant).

Horsepower:

Approx. 288-306 hp (DIN) depending on market and specific engine tune for the 5.0L S model.

Torque:

Approx. 317-343 lb-ft (430-465 Nm) depending on market and specific engine tune for the 5.0L S model.

Fuel Delivery:

Bosch L-Jetronic or KE-Jetronic (K-Jetronic with electronic control) fuel injection.

Fuel Type:

Unleaded Premium Gasoline (91+ octane recommended).

ECM Type:

Bosch Motronic or similar engine control module.

Emissions Control:

Catalytic Converter, Oxygen Sensors, EGR (Exhaust Gas Recirculation) system (market dependent).

🔧 Transmission

Type:

5-Speed Manual Transaxle (often designated G26/11 or similar).

Type:

3-Speed Automatic Transaxle (e.g., Automatic Sport-Tippshift).

Drive Layout:

Rear-wheel drive via transaxle (engine front, transmission rear).

Clutch Type:

Single dry plate, hydraulic actuation (manual transmission).

Manual Transmission Fluid:

API GL-4 SAE 75W-90 or SAE 80W-90 gear oil (check specific Porsche recommendations for exact spec).

Automatic Transmission Fluid:

Dexron III or equivalent ATF (Automatic Transmission Fluid).

📐 Dimensions

Length:

Approx. 4,655 mm (183.3 in)

Width:

Approx. 1,775 mm (69.9 in)

Height:

Approx. 1,280 mm (50.4 in)

Wheelbase:

Approx. 2,430 mm (95.7 in)

Curb Weight:

Approx. 1,560 kg (3,439 lbs) to 1,640 kg (3,616 lbs) depending on transmission and options.

Gross Vehicle Weight Rating:

Typically around 2,100 kg (4,630 lbs).

🛡️ Safety Features

Crash Test Data:

Limited official crash test data available for this era, but constructed with robust safety features for its time.

ABS:

Standard Anti-lock Braking System (ABS).

Braking System Front:

Internally vented discs, approx. 304 mm diameter.

Braking System Rear:

Internally vented discs, approx. 295 mm diameter.

Seatbelts:

Three-point inertia-reel seatbelts with pre-tensioners (likely standard for '88).

Airbags:

Driver-side airbag was introduced on later models; confirmation for the '88 model is advised. If present, the manual will cover its related wiring.

Body Construction:

High-strength steel chassis with aluminum body panels.

💡 Technology Features

Audio System:

Factory-installed AM/FM radio with cassette player, often with amplifier and speaker system. Wiring for these units is detailed in the manual.

ABS Functionality:

The manual details the ABS sensor wiring, control unit connections, and hydraulic modulator electricals.

Diagnostic Ports:

Early diagnostic capabilities might be limited to specific test points and component diagnostics rather than a universal OBD-II port.

🔧 Maintenance

Oil Change:

Typically every 7,500 miles (12,000 km) or annually, whichever comes first. Consult the specific owner's manual.

Major Service:

Timing belt replacement is critical and typically recommended every 50,000 miles (80,000 km) or 4-5 years. This manual may not detail timing belt replacement but highlights its electrical triggers.

Engine Oil:

API SJ/SL or higher, SAE 10W-40 or 15W-50. Porsche A40 approval recommended for optimal performance. Oil capacity approx. 8.5 liters (9.0 US quarts).

Coolant:

Porsche approved coolant or a high-quality ethylene glycol based coolant with corrosion inhibitors. Capacity approx. 10.5 liters (11.1 US quarts).

Brake Fluid:

DOT 4 specification, high-temperature brake fluid.

Electrical Gremlins:

Age-related degradation of wiring insulation, corroded connectors, failing relays (e.g., fuel pump relay, K-Jetronic relays), issues with the HVAC control panel, and the central locking system are common. This manual is essential for diagnosing these.

Fuel System Maintenance:

Regular cleaning/replacement of fuel injectors, fuel filter, and checking fuel pressure regulator operation.

Cooling System:

Leaking coolant hoses, failing water pump, and radiator issues can occur due to age.

📚 Vehicle History

Porsche Philosophy:

Porsche is renowned for performance, engineering precision, and motorsport heritage. The 928 was a significant, albeit controversial, diversification.

928 Development:

Conceived as a successor to the 911, offering a more comfortable and modern GT experience. Featured innovative technologies like the transaxle and advanced suspension for its time.

S Model Updates:

The 'S' designation indicated engine enhancements, including larger displacement and power output improvements over earlier models. The '88 model falls into the later S3/S4 evolutionary phase.

Production Years:

1978-1995

Manufacturing Location:

Stuttgart, Germany.

🏆 Awards & Recognition

Car Of The Year:

The Porsche 928 was awarded Motor Trend's Car of the Year in 1978.

Design Awards:

Received various design awards for its aerodynamic and futuristic styling.