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.
Competitors:
BMW 5 Series, Mercedes-Benz E-Class, Volvo 240/740/940 series, Saab 9000.
Audi Advancements:
Known for its aerodynamic styling, advanced Quattro all-wheel-drive system, and a focus on build quality and driver comfort.
Purpose:
To provide technicians and knowledgeable owners with the precise factory-level repair and maintenance procedures for the 1991 Audi 100/Avant.
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
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
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.
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)
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)
Injection:
Bosch KE-Jetronic CIS-E (CIS-Electronic Fuel Injection)
Fuel Type:
Unleaded Gasoline (Premium recommended)
Ignition:
Electronic Ignition system (e.g., Digifant or similar)
Emissions Control:
Catalytic Converter, Lambda Sensor (O2 sensor), EGR (Exhaust Gas Recirculation)
Standard Transmission:
5-speed Manual
Optional Transmission:
4-speed Automatic (ZF 4HP22)
Drivetrain Options:
Front-Wheel Drive (FWD) standard, Quattro All-Wheel Drive (AWD) optional on most models.
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)
Crash Test Era Context:
Testing standards in 1991 were less stringent than today; specific NCAP ratings are unlikely to be readily available but the vehicle was designed with European safety standards of the time in mind.
ABS:
Anti-lock Braking System (ABS) often standard or optional on higher trims/Quattro models.
Airbags:
Driver's airbag typically standard for 1991. Passenger airbag less common for this year/model.
Seatbelts:
Three-point inertia-reel seatbelts, height-adjustable front belts.
Body Structure:
Designed with crumple zones and a safety cage for occupant protection.
Audio System:
Factory-installed Audi sound systems, often with cassette player and AM/FM radio. Pre-wiring for CD changer might be present on later models.
ABS Implementation:
ABS was a significant technology for its time, improving braking stability and reducing stopping distances under hard braking.
Pre Wiring:
Limited by modern standards, but might have provisions for early cellular phones or aftermarket cruise control installations.
Power Accessories:
Power windows, power locks, and power mirrors were available, often standard on higher trims.
Oil Change Interval:
Typically every 10,000-15,000 km or 6-12 months (refer to manual for exact specification).
Timing Belt Replacement:
Critical component. Recommended replacement interval around 90,000 - 120,000 km or 5-7 years (highly important for the 5-cylinder engine).
Spark Plugs:
Check and replace as needed, typically every 30,000-60,000 km depending on type (e.g., standard copper vs. platinum).
Engine Oil Grade:
SAE 5W-30 or 5W-40 synthetic or semi-synthetic meeting API SG/SH specifications is common. Check manual for exact Audi approval.
Engine Oil Capacity:
Approx. 4.2 - 4.5 Liters (with filter)
Coolant Type:
G11 (blue/green) ethylene glycol-based coolant. Mixture ratio 50:50 with distilled water.
Brake Fluid Type:
DOT 3 or DOT 4.
Fuel System Reliability:
Bosch CIS-E can be sensitive to vacuum leaks; distributor rebuilds or seal replacements may be needed over time.
Electrical System:
Aging wiring harnesses, particularly grounds, and connector issues can lead to intermittent faults.
Suspension Bushings:
Worn suspension bushings (control arms, sway bars) are common due to age and mileage, impacting ride and handling.
Climate Control:
HVAC blower motor resistors, vacuum actuators for blend doors, and AC compressor clutch failures can occur.
Audi Legacy:
Audi's history is rooted in engineering excellence, particularly in quattro all-wheel drive technology and innovative drivetrain solutions.
Typ 4A Introduction:
The Typ 4A Audi 100 was introduced in late 1990 for the 1991 model year, replacing the Typ 44 (C3) generation. It featured a completely new platform and design.
Design Philosophy:
Emphasis on aerodynamics (hence '100' signifying its aerodynamic drag coefficient), comfort, and advanced technology for its time.
Manufacturing Location:
Ingolstadt, Germany
Generations Impact:
This generation (Typ 4A) laid the groundwork for the subsequent Audi A6, showcasing Audi's emerging design language and technological prowess.
