Market Position:
The Mitsubishi Sigma, known in some markets as the Mitsubishi Diamante, was positioned as a mid-size luxury sedan/coupe, competing with established players like the Toyota Camry/Lexus ES, Honda Accord/Acura Vigor, and Nissan Maxima/Infiniti J30. It offered a blend of performance, comfort, and distinctive styling.
Competitive Analysis:
The Sigma aimed to differentiate itself through its advanced (for the time) V6 engine options, sophisticated available all-wheel-drive (AWD) system, and a premium interior. Its styling was often considered more angular and assertive than some competitors.
Key Features:
Available V6 engines, Optional All-Wheel Drive (AWD), Independent Rear Suspension, Available Anti-lock Braking System (ABS), Premium Interior Appointments, Sophisticated Styling.
Coverage Areas:
Mechanical, Electrical, Body, Chassis, Diagnostics, Maintenance, Repair, Troubleshooting
Trim Levels Covered:
ES, ES-S, GSi, GSi-S, and any other regional trim variations present during the 1991-1995 model years.
Page Count:
Approximately 1200+
Manual Type:
Workshop Manual / Service Manual
Format:
Digital (likely PDF, printable)
Systems Covered:
Engine Mechanical, Engine Control System (ECU), Fuel System, Ignition System, Cooling System, Lubrication System, Exhaust System, Automatic Transmission, Manual Transmission, Drivetrain (FWD/AWD), Suspension (Front & Rear), Steering System, Braking System (ABS), Climate Control System, Electrical System (Wiring Diagrams), Lighting System, Audio System, Body & Trim, Body Control Module (BCM), SRS Airbag System
Procedures Included:
Routine Maintenance, Scheduled Servicing, Engine Overhaul, Transmission Service, Brake Repair, Suspension Component Replacement, Steering System Alignment, Electrical Diagnostics & Repair, HVAC System Service, Body Panel Repair, Interior Trim Removal/Installation, Fuel System Cleaning & Repair, Cooling System Flush, Exhaust System Repair, Tire Rotation & Balancing, Wheel Alignment, Clutch Replacement, Drive Axle Service, SRS System Diagnostics
Technical Depth:
Comprehensive: From basic fluid changes and component replacement to in-depth engine rebuilds, transmission overhauls, and complex electrical system diagnostics. Includes detailed troubleshooting charts, diagnostic trouble codes (DTCs), specifications, and procedures.
Diagnostic Procedures:
Detailed procedures for diagnosing engine performance issues, transmission problems, electrical faults, and HVAC system malfunctions. Includes diagnostic trouble code (DTC) interpretation for OBD-I systems.
Wiring Diagrams Completeness:
Includes comprehensive, schematics for all major electrical systems, including engine management, lighting, power accessories, audio, and safety systems.
Primary Engine:
3.0L SOHC V6 (6G72)
Engine Variants:
2.0L SOHC I4 (4G63), 2.5L SOHC V6 (6G73), 3.0L SOHC V6 (6G72), 3.0L DOHC V6 (6G72) (in some higher trims/markets)
2.0L I4 Horsepower:
Approx. 133 hp @ 6000 RPM
2.5L V6 Horsepower:
Approx. 170 hp @ 6000 RPM
3.0L Sohc V6 Horsepower:
Approx. 195 hp @ 6000 RPM
3.0L DOHc V6 Horsepower:
Approx. 210 hp @ 6000 RPM
Torque Figures:
Varies by engine. E.g., 3.0L SOHC V6: Approx. 205 lb-ft @ 4500 RPM.
Fuel System:
Electronic Fuel Injection (EFI), Multi-port Fuel Injection (MPI)
Cooling System Type:
Pressurized, liquid-cooled
Lubrication System Type:
Forced lubrication with oil pump and filter
Emissions Control Features:
Catalytic Converter, Exhaust Gas Recirculation (EGR), Oxygen Sensors
Standard Transmission:
4-Speed Automatic Transmission
Optional Transmission:
5-Speed Manual Transmission (less common, often paired with I4 or smaller V6)
Transmission Features:
Sportronic (sequential shifting) on some automatic models, Electronic Control Unit (ECU) management for shift points, available All-Wheel Drive (AWD) system (often designated as 'ECS' or similar).
Automatic Transmission Fluid Spec:
Diamond SP III or equivalent DEXRON III/MERCON
Automatic Transmission Fluid Capacity:
Approx. 7.5 - 8.5 Liters (dry fill)
Wheelbase:
Approx. 110.2 inches (2799 mm)
Length:
Approx. 191.3 inches (4860 mm)
Width:
Approx. 70.5 inches (1790 mm)
Height:
Approx. 56.3 inches (1430 mm)
Curb Weight:
Approx. 3300 - 3700 lbs (1497 - 1678 kg), depending on configuration.
Gross Vehicle Weight Rating:
Typically around 4500 - 4800 lbs (2041 - 2177 kg).
Trunk Volume:
Approx. 15.5 cubic feet (0.44 cubic meters)
Wheel Bolt Pattern:
5x114.3 mm (5x4.5 inches)
Standard Tire Size:
P205/60R15 or P215/55R16 (depending on trim and year)
Safety Ratings:
Likely received average to good safety ratings for its era. Specific NHTSA/IIHS ratings may vary by market and specific year/configuration.
Active Features:
Optional Anti-lock Braking System (ABS), Traction Control (on some AWD models), Variable Assist Power Steering.
Passive Features:
Driver and Passenger Front Airbags (standard on most models from 1992 onwards), Side Impact Door Beams, Crumple Zones, Pretensioner Seatbelts.
Child Safety Features:
Rear Door Child Safety Locks, Child Seat Anchors (LATCH system not standard, likely ISOFIX equivalents in some markets or aftermarket additions).
Infotainment Features:
Factory installed AM/FM Stereo with Cassette Player, Optional CD Player, Optional premium audio systems (e.g., Mitsubishi Premium Sound), Manual climate control or optional automatic climate control.
Driver Assistance Features:
Optional ABS, Cruise Control, Power windows and locks, Keyless entry (on later models/higher trims).
Connectivity Features:
Limited by era. Primarily focused on the vehicle's internal systems. No integrated Bluetooth or smartphone connectivity.
Lighting Features:
Halogen headlights, Fog lights (optional), Power adjustable headlights.
Oil Change Interval:
Every 3,750 miles (6,000 km) or 3 months for severe conditions, 7,500 miles (12,000 km) or 6 months for normal conditions (refer to manual for precise recommendation).
Timing Belt Replacement Interval:
Every 60,000 miles (96,000 km) for V6 engines (critical interval, interference design).
Coolant Flush Interval:
Every 30,000 miles (48,000 km) or 2 years.
Transmission Fluid Change Interval:
Every 30,000 miles (48,000 km) or 2 years.
Engine Oil Spec:
API SG or SH, SAE 5W-30 or 10W-30 (check owner's manual for ambient temperature suitability).
Coolant Spec:
Mopar Antifreeze/Coolant (Chrysler formulation) or equivalent (long-life, green type) - 50/50 mix with distilled water.
Power Steering Fluid Spec:
Dexron II/III ATF or specific power steering fluid.
Brake Fluid Spec:
DOT 3 or DOT 4.
Known Issues:
Timing belt failure (critical on V6 engines, can cause catastrophic damage), Crankshaft position sensor failures, Automatic transmission solenoid issues, EGR valve clogging, Rust on wheel arches and rocker panels, Door lock actuator failure, Condensation in headlights, Heater core leaks.
Oil Filter Part Number Example:
Wix 51540, Fram PH3569, Bosch 3323 (verify for specific engine).
Air Filter Part Number Example:
Wix 42756, Fram CA3984 (verify for specific engine).
Spark Plug Recommendation:
NGK BKR5EKU or equivalent (iridium plugs recommended for longer life, refer to manual for exact spec).
Brand Heritage:
Mitsubishi Motors, a division of Mitsubishi Group, has a long history in automotive manufacturing, known for engineering innovation and a focus on performance and durability, particularly in its rally heritage.
Model Evolution:
The Sigma was part of Mitsubishi's effort to compete in the growing mid-size sedan and coupe market. It shared platforms and components with the Diamante, which was more widely marketed globally. The second generation (1991-1995) saw refinement in styling and technology.
Production Locations:
Primarily manufactured in Japan.
Production Years:
1990-1996 (Global Model Lifespan for this generation)
