Positioning:
Jeep vehicles in 1990 were positioned as robust, capable off-road vehicles and practical utility vehicles. The Cherokee (XJ) was a pioneer in the compact SUV segment, known for its unibody construction and legendary four-wheel-drive systems. The Wrangler (YJ) continued the legacy of the CJ series with its iconic open-air, go-anywhere design. The Grand Cherokee (ZJ), introduced later in the decade, aimed at a more premium segment of the SUV market.
Competitors:
In 1990, the Cherokee competed with vehicles like the Ford Bronco II, Chevrolet S-10 Blazer, and Toyota 4Runner. The Wrangler competed primarily against itself as the segment leader and other niche off-roaders. The upcoming Grand Cherokee would face competition from luxury SUVs such as the Lincoln Navigator and Cadillac Escalade, and established players like the Range Rover and Mitsubishi Montero.
Jeep Cherokee Xj:
Compact SUV, unibody construction, strong off-road capability, available 4.0L inline-six engine, spacious interior for its size, practical for daily use.
Jeep Wrangler Yj:
Body-on-frame construction, removable doors and top, iconic Jeep styling, strong off-road performance, basic amenities, designed for open-air driving and recreation.
Manual Purpose:
To provide professional automotive technicians with the necessary information to diagnose, maintain, and repair Jeep vehicles manufactured by Chrysler Motors for the 1990 model year, ensuring accuracy and efficiency in service operations.
Powertrain:
Engine mechanical (4.0L I6, 2.5L I4), fuel system (injection and carburetion where applicable), ignition system, exhaust system, cooling system, lubrication system, powertrain control module (PCM) and diagnostics.
Transmission And Drivetrain:
Manual and automatic transmissions (e.g., AX-5, AX-15, AW-4), transfer case operation and repair, front and rear axle assemblies, drive shafts, U-joints, driveline diagnostics and repair.
Braking System:
Front and rear brake systems (disc and drum), hydraulic system, parking brake, ABS system (if equipped), bleeding procedures, component replacement.
Suspension And Steering:
Front and rear suspension systems (leaf spring, coil spring, solid axle designs), steering linkage, power steering system, wheel alignment specifications.
Electrical System:
Battery, charging system (alternator), starting system (starter motor), lighting system, instrumentation, power accessories (windows, locks), wiring diagrams, fuse and relay locations, diagnostic procedures for electrical faults.
Body And Chassis:
Frame construction, body panels, doors, interior trim, HVAC system (heating, ventilation, and air conditioning), glass replacement, body sealing, chassis lubrication.
Diagnostics And Troubleshooting:
Diagnostic trouble codes (DTCs), symptom-based troubleshooting guides, diagnostic tools and procedures, component testing methods.
Routine Maintenance:
Oil and filter changes, air filter replacement, spark plug replacement, fluid level checks and top-offs, lubrication points.
Component Replacement:
Detailed step-by-step instructions for replacing major components like engine parts, transmission units, brake calipers, suspension arms, alternators, starters, fuel pumps, etc.
Overhaul And Rebuild:
Instructions for overhauling or rebuilding engines, transmissions, transfer cases, and differentials, including torque specifications and assembly sequences.
Electrical System Repair:
Diagnosis and repair of wiring harnesses, sensors, actuators, and control modules, including interpretation of wiring diagrams.
Bodywork And Interior:
Procedures for body panel alignment, door adjustments, interior trim removal and installation, HVAC component replacement.
Special Tools:
Identification and usage instructions for specialized tools required for specific repair or diagnostic procedures.
Troubleshooting Electrical:
Detailed diagnostic charts and flowcharts for identifying and resolving electrical system faults, including starter, charging, lighting, and accessory issues.
Engine Tuning:
Procedures for ignition timing adjustment (if applicable, though most systems were distributorless by then or had electronic timing control), fuel system adjustments, and emission control system checks.
Depth:
Comprehensive. Designed for professional technicians, it provides in-depth diagnostic procedures, detailed component specifications, overhaul instructions, and complete repair sequences, covering everything from basic tune-ups to full engine rebuilds and complex electrical system diagnostics.
Engine 4.0L I6:
4.0L (242 ci) AMC I6. Known for its durability, torque, and smooth operation. Often referred to as the 'PowerTech' or 'High Output' six-cylinder.
Engine 2.5L I4:
2.5L (150 ci) AMC I4. A simpler, more fuel-efficient option, though less powerful than the 4.0L. Primarily found in base model Cherokees.
4.0L I6 Horsepower:
Approximately 173-177 hp @ 4500-4700 rpm (actual figures may vary slightly by specific application within the 1990 model year).
4.0L I6 Torque:
Approximately 220-225 lb-ft @ 3200-3300 rpm.
2.5L I4 Horsepower:
Approximately 121-130 hp @ 4800-5000 rpm.
2.5L I4 Torque:
Approximately 145-150 lb-ft @ 2400-2500 rpm.
Fuel Injection:
Multi-point fuel injection (MPI) for the 4.0L I6 and likely for the 2.5L I4 by 1990. Early models or specific variants might have had Throttle Body Injection (TBI) or even carburetion on very early 4.2L engines if still in production for certain markets.
Fuel Type:
Unleaded gasoline, 87 octane recommended.
Coolant Type:
Ethylene Glycol based coolant, typically a 50/50 mix with distilled water.
Transmission Options:
Available with both manual and automatic transmissions depending on the model and trim level.
Manual Transmission Yj:
AX-5 5-speed manual (common in base models and 4-cylinders).
Manual Transmission Xj:
AX-15 5-speed manual (typically with 4.0L engines, known for its robustness).
Automatic Transmission:
AW-4 4-speed automatic (sourced from Aisin-Warner, known for its reliability and smooth shifting, common with the 4.0L).
Transfer Case:
Command-Trac (242) or Selec-Trac (231) full-time 4WD systems for Cherokee, NP231 or NP242 transfer cases were common. Wrangler YJ typically featured the NP231 part-time transfer case.
Transmission Fluid Type:
Automatic Transmission Fluid (ATF+3 or equivalent) for AW-4; Manual transmission fluid (GL-3 or GL-4) for manual gearboxes.
Crash Test Results:
NHTSA ratings for 1990 models are generally available but may vary. Vehicles of this era did not have the advanced safety structures or testing protocols of modern vehicles. Specific ratings should be verified for individual models.
ABS:
Anti-lock Braking System (ABS) was an optional feature, typically available on higher trim levels and specific models.
Four Wheel Drive:
The full-time and part-time 4WD systems provided enhanced traction and control, contributing to active safety in adverse conditions.
Seat Belts:
Three-point seat belts for front occupants, lap belts for rear occupants. Shoulder belts were standard on front seats.
Airbags:
Driver-side airbags were not standard or widely available on 1990 Jeep models; passenger airbags were not offered.
Rollover Protection:
The Wrangler YJ, due to its open-top design, had a certified roll bar behind the front seats for basic rollover protection. The Cherokee XJ's unibody structure offered more integrated protection.
Audio System:
Basic AM/FM stereo with cassette player was standard. Optional upgrades included premium sound systems with more speakers and graphic equalizers.
Gauges And Displays:
Analog gauges for speedometer, tachometer (optional on some models), fuel, engine temperature, oil pressure, and voltmeter. Warning lights for various systems.
Cruise Control:
Optional feature on most models, providing convenience for highway driving.
Power Accessories:
Power windows, power door locks, and power mirrors were available as optional equipment on higher trim levels.
OBD System:
OBD-I (On-Board Diagnostics, First Generation) system. Diagnostic procedures involve reading trouble codes via jumper wires or specialized scanners designed for the OBD-I interface.
Oil Change Interval:
Every 3,000-5,000 miles (4,800-8,000 km) or every 6 months, whichever comes first. Consult specific manual for engine oil type and capacity.
Transmission Fluid Change:
Automatic transmissions: 30,000-60,000 miles (48,000-96,000 km). Manual transmissions: Check fluid level periodically, replacement at higher mileage (e.g., 80,000-100,000 miles).
Spark Plug Replacement:
4.0L I6: Approximately 30,000-60,000 miles. 2.5L I4: Similar or slightly longer intervals depending on plug type.
Coolant Flush:
Every 2-3 years or 30,000-50,000 miles.
Engine Oil Viscosity:
Typically 10W-30 for both 4.0L and 2.5L engines. May specify 5W-30 for colder climates.
Engine Oil Capacity:
4.0L I6: Approximately 5 quarts (4.7 liters) with filter. 2.5L I4: Approximately 4 quarts (3.8 liters) with filter.
Brake Fluid Type:
DOT 3 brake fluid.
Cherokee Xj Common Problems:
Cracked cylinder heads (particularly early 4.0L engines, though less common by 1990), differential pinion seal leaks, worn steering components (track bar, ball joints), water pump leaks, alternator failures, rust in common areas (rocker panels, wheel wells).
Wrangler Yj Common Problems:
Leaf spring perches cracking (off-road use), steering box wear, rear main seal leaks (4.0L), dashboard electrical issues, exhaust manifold cracks (4.0L), fuel pump failures, rust.
Hvca Issues:
Blend door actuator failures in HVAC systems, AC compressor failures, heater core leaks.
Jeep Legacy:
Jeep's heritage dates back to World War II with the Willys MB. The brand is synonymous with ruggedness, off-road capability, and utility. Chrysler acquired American Motors Corporation (AMC), Jeep's parent company, in 1987, integrating Jeep into its product portfolio.
Cherokee Xj Development:
The XJ Cherokee, introduced in 1984, was revolutionary for its time as one of the first compact SUVs built with unibody construction, setting it apart from body-on-frame competitors. It offered a balance of utility, comfort, and off-road prowess.
Wrangler Yj Development:
The YJ Wrangler replaced the CJ-7 in 1986. It featured a revised chassis, updated suspension (leaf springs at all four corners), and squared-off headlights, a significant departure from the iconic round headlights of previous Jeeps, which was a point of contention among enthusiasts.
Manufacturing Locations:
Primary assembly plants included Toledo, Ohio, and Brampton, Ontario, Canada.
