🏷️ Basic Information

Make:

Audi

Model:

100

Year:

1991

Chassis Code:

C4-4A

👋 Introduction

Segment:

Executive Sedan / Luxury Mid-size Sedan

Brand Perception:

Premium, advanced engineering, quattro all-wheel drive reputation

Key Competitors 1991:

BMW 5 Series (E34), Mercedes-Benz E-Class (W124), Lexus LS 400 (though higher segment), Cadillac DeVille

Drivetrain Options:

Front-wheel drive (FWD) and permanent all-wheel drive (quattro)

Platform Design:

C4 platform, known for robust construction and aerodynamic styling

Interior Quality:

High-quality materials, ergonomic design, advanced features for its time

📋 Manual Details

All Models Variants:

Yes

Repair Scope:

A-Z (All Repairs)

Estimated Pages:

Extensive (typical for factory service manuals, often 1000+ pages)

Type:

Factory Service Manual (FSM)

Language:

English

Format:

PDF Download

📖 Manual Coverage

Powertrain:

Engine mechanical, engine electrical, fuel system, ignition system, exhaust system, transmission (manual and automatic), drivetrain, clutch

Chassis:

Suspension (front and rear), steering system, braking system (including ABS), wheels and tires

Body And Interior:

Body construction, exterior trim, doors, windows, interior trim, seats, climate control system (HVAC), audio system

Electrical And Electronics:

Wiring diagrams, lighting, instruments, charging system, starting system, power accessories, control modules, diagnostic trouble codes (DTCs)

Maintenance:

Scheduled maintenance, fluid changes, filter replacements, lubrication, inspections

Repair And Rebuild:

Engine overhaul, transmission overhaul, component replacement, system diagnostics, electrical repairs, body panel repair

Diagnostics And Troubleshooting:

Step-by-step diagnostic procedures, fault finding charts, symptom-based troubleshooting

Depth:

Comprehensive; covers basic maintenance to complete engine and transmission rebuilds, including detailed electrical schematics and diagnostic procedures

📊 Manual Specifications

Digital Format:

PDF

Scan Quality:

High-resolution (assumed, based on description of dealership use)

Binding:

N/A (Digital PDF Download)

Paper Quality:

N/A (Digital PDF Download)

⚙️ Engine Specifications

Engine Code And Type:

AAH (2.8L SOHC V6 90°)

Displacement Liters:

2.8

Horsepower Ps:

172 PS @ 5500 rpm (approximate, varies slightly by market/spec)

Torque Nm:

245 Nm @ 3000 rpm (approximate)

Fuel System:

Bosch Motronic fuel injection (typically Motronic M2.3 or M2.4)

Ignition System:

Electronic ignition with distributor

Valve Train:

SOHC (Single Overhead Camshaft) per bank, 2 valves per cylinder

Engine Options:

5-cylinder gasoline engines (e.g., 2.3E, 2.3E-20V), 5-cylinder diesel engines (e.g., 2.5 TDI), 2.2L 5-cylinder gasoline (prior to C4 in some markets), potentially turbo variants in some regions (e.g., S4 variants).

🔧 Transmission

Transmission Options:

5-speed manual transmission

Transmission Options:

4-speed automatic transmission (ZF 4HP22 or similar)

AWD System:

Torsen T-3 center differential for quattro models, typically with rear open differential (early models) or optional rear limited-slip differential (LSD).

Manual Transmission Fluid Spec:

API GL-4 or GL-5, SAE 75W-90 (Check manual for exact spec)

Automatic Transmission Fluid Spec:

G 052 162 A1 (or equivalent Dexron-III compatible fluid, consult manual for specific Audi specification)

📐 Dimensions

Length Mm:

4787 mm (approx.)

Width Mm:

1778 mm (approx.)

Height Mm:

1430 mm (approx.)

Curb Weight Kg:

1450 - 1600 kg (depending on engine and drivetrain)

Gross Vehicle Weight Rating Kg:

Approx. 2000 - 2150 kg

Trunk Volume Liters:

Approximately 550 liters (sedan)

🛡️ Safety Features

Crash Test Data Availability:

Limited public data for 1991 models, but designed to meet European safety standards of the era.

ABS:

Anti-lock Braking System (ABS) available/standard on many models

Traction Control:

Traction Control System (ASR - Automatic Slip Regulation) available on some quattro models

Airbags:

Driver-side airbag standard on many models, passenger airbag optional or unavailable depending on market and configuration.

Seatbelts:

Front and rear seatbelts, pre-tensioners for front seatbelts on some models

Body Structure:

Integrated safety cage, crumple zones

💡 Technology Features

Audio System:

Factory AM/FM stereo cassette player, optional CD player, often with premium speaker systems (e.g., Bose on higher trims).

Climate Control Tech:

Manual or optional automatic climate control (Climatronic).

Cruise Control:

Standard or optional cruise control

Connectivity Features:

N/A (No modern connectivity features like Bluetooth or USB)

Headlights:

Halogen headlights, aerodynamic design for the era.

🔧 Maintenance

Oil Change Interval:

Typically 10,000 km or 6 months (whichever comes first), though consult the specific manual for precise intervals and oil type.

Spark Plug Replacement:

e.g., 30,000 - 60,000 km depending on plug type (e.g., copper vs. platinum/iridium).

Timing Belt Replacement:

Crucial for V6 and 5-cylinder engines. Typically 60,000 - 90,000 km or 5-7 years. Failure causes catastrophic engine damage.

Diesel Fuel Filter:

Recommended replacement every 20,000 - 40,000 km

Engine Oil Spec:

VW 500 00, 501 01, or 502 00 (depending on specific engine and oil formulation), typically SAE 5W-40 or 10W-40. Consult manual for exact spec.

Coolant Spec:

G 11 specification (blue/green coolant), often a 50/50 mix with distilled water.

Brake Fluid Spec:

DOT 3 or DOT 4

Engine Mechanical:

Timing belt failure (critical), oil leaks from seals and gaskets (valve cover, oil pan), potential for head gasket issues with age.

Electrical:

Degradation of wiring insulation (especially around engine bay), failure of dashboard illumination, HVAC control issues, central locking problems, vacuum hose degradation affecting climate control.

Suspension:

Worn control arm bushings, ball joints, tie rod ends, rear torsion beam bushings (if applicable), strut/shock absorber wear.

Fuel System:

Clogged fuel injectors, failing fuel pumps, aging fuel lines.

Climate Control:

Vacuum leaks affecting mode control, blower motor resistor failure, compressor clutch issues.

📚 Vehicle History

Audi Heritage:

Founded in 1910, known for engineering innovation, advanced automotive technology, and performance.

Audi 100 Evolution:

The C4 generation, launched in 1991, represented a significant redesign from the C3, featuring a more rounded, aerodynamic body, improved interior, and upgraded powertrain options, including the introduction of the V6 engine as a primary offering.

Production Period:

1991 - 1994 (for C4 generation Audi 100)

Manufacturing Locations:

Germany (primary), also potentially in other Volkswagen Group facilities.

Evolution To A6:

The C4 generation Audi 100 was facelifted and renamed Audi A6 in 1994, marking a shift in Audi's naming convention.

🏆 Awards & Recognition

Industry Recognition:

The C4 generation was generally well-regarded for its build quality, driving dynamics (especially quattro models), and comfort, often reviewed favorably against its German and Japanese luxury competitors.

Reliability Perception:

Mixed; while mechanically robust, complex European electronics can be a source of issues if not maintained. Critical to adhere to maintenance schedules, especially for the timing belt.