This manual provides comprehensive service and repair information for the 1990 Audi 100 (C4-4A), encompassing all sedan and Avant variants. Representing sophisticated German engineering, the Audi 100 of this era was positioned as a premium mid-size executive vehicle, known for its refined interior, robust build quality, and the availability of the renowned Quattro all-wheel-drive system. This generation, produced from 1990 to 1994, featured sleeker styling and improved aerodynamics, offering a compelling alternative to established European luxury sedans. The vehicle’s engineering philosophy emphasized driver comfort and performance, with available five-cylinder engines and advanced fuel injection systems of the time. This Service and Repair Manual is designed to assist professional technicians and experienced DIY enthusiasts in maintaining and repairing the 1990 Audi 100. It covers a vast range of systems, including engine mechanicals, fuel injection, ignition, cooling, lubrication, transmission (manual and automatic), driveline, suspension, steering, braking systems (including ABS), and electrical systems. Detailed procedures for routine maintenance, complex repairs, and systematic troubleshooting are provided, along with essential technical specifications, torque values, and diagnostic charts. With over 1000 pages of dealership-level technical data, this manual is an indispensable resource for ensuring the optimal performance and longevity of your Audi 100. 🏷️ Basic Information Identification Make: Audi Model: 100 Year: 1990 Codes Chassis Code: C4-4A 👋 Introduction Market Position Segment: Mid-size executive sedan and wagon, positioned as a premium European alternative. Competitive Analysis Competitors: BMW 5 Series, Mercedes-Benz E-Class, Volvo 740/940, Saab 9000. Key Features Design Philosophy: Sophisticated German engineering, Quattro all-wheel-drive availability, refined interior, and strong build quality. 📋 Manual Details Coverage Areas Primary Coverage: Comprehensive service and repair for the 1990 Audi 100 (C4-4A). Model Variants Covered: All models and configurations of the 1990 Audi 100 (C4-4A) including sedan and Avant variants. Page Count Estimated Page Count: 1000+ Manual Type Type: Service and Repair Manual Purpose: Designed for professional technicians and experienced DIY enthusiasts. Content Focus: Technical service data, repair instructions, diagnostic procedures, specifications, and torque values. Language Language: English Format Format: PDF Download 📖 Manual Coverage Systems Covered Engine Systems: Engine mechanical (block, head, pistons, crankshaft, camshafts), fuel injection (CIS-E, KE-Jetronic), ignition, cooling, lubrication, exhaust, emissions control. Transmission Systems: Manual and automatic transmission overhaul, clutch, driveline, CV joints, differentials. Chassis And Suspension: Front and rear suspension, steering system, wheel bearings, shock absorbers, springs, bushings. Brake Systems: Hydraulic brake system, ABS (Anti-lock Braking System), brake pads, rotors, calipers, lines, master cylinder. Electrical Systems: Wiring diagrams, starter, alternator, battery, lighting, instruments, dashboard controls, fuses, relays, onboard diagnostics (OBD). Body And Interior: Body panels, doors, locks, hinges, glass, upholstery, climate control, HVAC, seat adjustments. Cooling System: Radiator, water pump, thermostat, heater core, fan operation, coolant flush procedures. Lubrication System: Oil pump, oil filter housing, oil pan, oil cooler (if equipped). Ignition System: Distributor, ignition coil, spark plug wires, spark plugs, ignition control module (ECU). Procedures Included Maintenance Procedures: Routine maintenance checks, oil changes, filter replacements, fluid level checks, belt inspections and replacement, spark plug replacement. Repair Procedures: Engine rebuilds, transmission repairs, suspension component replacement, brake service, electrical component diagnosis and repair, body panel repair. Troubleshooting Diagnostics: Systematic diagnostic procedures, fault code interpretation, symptom-based troubleshooting for all major vehicle systems. Bodywork Repair: Panel alignment, rust repair techniques, body trim removal and installation, window sealing. Diagnostic Charts: Detailed fault-finding charts correlating symptoms to potential causes and diagnostic steps. Technical Depth Depth: In-depth, dealership-level technical information covering complete overhauls, complex diagnostics, and specialized repair procedures. 📊 Manual Specifications File Format File Type: PDF Print Quality Resolution: High-resolution scans for clear text and legible diagrams. Binding Type Binding Type: N/A (Digital PDF) Paper Type Paper Type: N/A (Digital PDF) ⚙️ Engine Specifications Primary Engine Engine Code Common: Various, including 5-cylinder variants (e.g., 2.3L, 2.2L Turbo). Engine Displacement Example: 2.3 Liters (2309 cc) Engine Configuration Example: Inline 5-cylinder, SOHC or DOHC Performance Example Horsepower Example: ~130 hp @ 5500 rpm (2.3E) Torque Example: ~137 lb-ft @ 3000 rpm (2.3E) Fuel System Fuel Delivery: Bosch CIS-E (Continuous Injection System - Electronic) or KE-Jetronic fuel injection. Fuel Type: Unleaded Gasoline 🔧 Transmission Standard Transmission Type Standard: 5-speed Manual Transmission Optional Transmission Type Optional: ZF 4-speed Automatic Transmission (e.g., 4HP22) Features Drivetrain Options: Front-wheel drive (FWD) and permanent all-wheel drive (Quattro). 📐 Dimensions Exterior Sedan Example Length: Approx. 4770 mm (187.8 in) Width: Approx. 1777 mm (70.0 in) Height: Approx. 1420 mm (55.9 in) Wheelbase: Approx. 2700 mm (106.3 in) Weights Example Curb Weight: Approx. 1400-1500 kg (3086-3307 lbs) 🛡️ Safety Features Ratings Crash Test Data: While specific ratings for the 1990 model may be limited by modern standards, the C4 platform was known for robust construction. Active Features ABS: Optional Anti-lock Braking System (ABS) on many models. Passive Features Airbags: Driver's airbag standard on later models of this generation, passenger airbag optional. Seatbelts: Three-point inertia reel seatbelts with pre-tensioners. 💡 Technology...