The 1991 Audi 100 and 100 Avant represent Audi's commitment to sophisticated engineering and design within the executive mid-size luxury segment. These vehicles, built on the Typ 4A chassis, are distinguished by their aerodynamic styling, advanced Quattro all-wheel-drive system, and a focus on driver comfort and build quality. Powered by a 2.3-liter inline 5-cylinder engine, these Audis offered a blend of performance and refinement, competing with established European luxury brands. Their introduction marked a significant step forward for Audi, laying the foundation for future models and showcasing the brand's evolving design language and technological prowess. This comprehensive service and repair manual provides detailed, vehicle-specific information for all 1991 Audi 100 and 100 Avant models. It covers a wide range of systems, including engine mechanicals, fuel injection, transmissions (manual and automatic), drivetrain, suspension, brakes, steering, and electrical systems, as well as bodywork and HVAC. The manual includes essential procedures for scheduled maintenance, diagnostics, component repair, and technical specifications such as torque values and fluid capacities. Its purpose is to equip technicians and owners with the knowledge necessary for accurate diagnosis, effective repair, and proper maintenance, ensuring the longevity and optimal performance of these vehicles. 🏷️ Basic Information Identification Make: Audi Model: 100 / 100 Avant Year: 1991 Chassis Codes: 4A (Sedan), 4A2 (Sedan), 2A5 (Avant - likely an internal or variant code, 4A chassis generally applies to Avant as well) Market Segment: Executive/Mid-size Luxury 👋 Introduction Market Position Positioning: The Audi 100 (Typ 4A) represented Audi's entry into the more premium mid-size sedan and wagon segment, competing with established European luxury brands. Competitive Analysis Competitors: BMW 5 Series, Mercedes-Benz E-Class, Volvo 240/740/940 series, Saab 9000. Key Features Audi Advancements: Known for its aerodynamic styling, advanced Quattro all-wheel-drive system, and a focus on build quality and driver comfort. Manual Purpose Purpose: To provide technicians and knowledgeable owners with the precise factory-level repair and maintenance procedures for the 1991 Audi 100/Avant. 📋 Manual Details Coverage Areas Primary Coverage: All 1991 Audi 100 and 100 Avant models Repair Scope: Comprehensive A-Z, vehicle-specific Page Count Estimated Page Count: Likely 800-1200+ pages (typical for comprehensive dealer-level manuals of this era) Manual Type Type: Service and Repair Manual Language Language: English Format Format: Print 📖 Manual Coverage Systems Covered Engine: Engine mechanical, diagnostics, fuel injection, ignition, emissions, cooling, lubrication, timing Transmission: Manual and Automatic transmission overhaul, diagnostics, operation, fluids Drivetrain: Front-wheel drive, Quattro all-wheel drive system (differentials, driveshafts, hubs) Suspension: Front and rear suspension components, alignment, shocks, springs, bushings Brakes: Hydraulic system, ABS (if equipped), brake pads, rotors, calipers, lines, master cylinder Steering: Power steering system, steering rack, tie rods, column Electrical: Complete wiring diagrams, starter, alternator, battery, lighting, instruments, power windows, locks, mirrors, climate control electronics Body: Body panel removal/installation, interior trim, glass, seals, chassis components HVAC: Heating, Ventilation, and Air Conditioning system operation, diagnostics, component replacement Procedures Included Maintenance: Scheduled maintenance, fluid changes, filter replacements, tune-ups Diagnostics: Troubleshooting guides, symptom-based diagnostics, fault code interpretation (OBD I era) Repair: Component disassembly, reassembly, adjustment, and replacement for all systems Technical Specifications: Torque specifications, clearances, fluid capacities, electrical resistance values Technical Depth Depth: Dealer-level comprehensive, covering everything from routine maintenance to full engine and transmission rebuilds. Diagnostic Tools: Information on necessary special tools and diagnostic equipment for effective repair. 📊 Manual Specifications File Format Format: Printed Publication Print Quality Quality: High-quality, durable paper stock, clear diagrams and text. Binding Type Binding: Likely a sturdy comb or perfect binding, designed for workshop use. Paper Type Paper Quality: Durable, often coated paper to resist grease and workshop grime. ⚙️ Engine Specifications Primary Engine Engine Type: Inline 5-cylinder, naturally aspirated Displacement: 2.3 Liters (2309 cc) Bore X Stroke: 76.4 mm x 101.0 mm Compression Ratio: 10.0:1 (typical) Performance Horsepower: 130 PS (96 kW) @ 5,500 rpm (typical for the 2.3E) Torque: 182 Nm (134 lb-ft) @ 4,000 rpm (typical for the 2.3E) Fuel System Injection: Bosch KE-Jetronic CIS-E (CIS-Electronic Fuel Injection) Fuel Type: Unleaded Gasoline (Premium recommended) Engine Management Ignition: Electronic Ignition system (e.g., Digifant or similar) Emissions Control: Catalytic Converter, Lambda Sensor (O2 sensor), EGR (Exhaust Gas Recirculation) 🔧 Transmission Standard Standard Transmission: 5-speed Manual Optional Optional Transmission: 4-speed Automatic (ZF 4HP22) Features Drivetrain Options: Front-Wheel Drive (FWD) standard, Quattro All-Wheel Drive (AWD) optional on most models. Fluid Type Automatic Transmission Fluid: Dexron III or equivalent (refer to manual for specific Audi part number) Manual Transmission Fluid: Gear Oil GL-4 75W-90 or similar (refer to manual) Differential Fluid: API GL-5 75W-90 or similar (refer to manual) 📐 Dimensions Exterior Length: Approx. 4790 mm (Sedan) / 4817 mm (Avant) Width: Approx. 1778 mm Height: Approx. 1410 mm (Sedan) / 1450 mm (Avant) Wheelbase: Approx. 2760 mm Wheel Bolt Pattern: 5x112 Weights Curb Weight: Approx. 1450-1550 kg (depending on drivetrain and equipment) Gross Vehicle Weight: Refer to vehicle's VIN plate/sticker 🛡️ Safety...