The 1990 Mercury Grand Marquis Service and Repair Manual is a practical, workshop-ready reference for maintenance, diagnostics, and repairs. Use it to troubleshoot symptoms, follow step-by-step procedures, verify specifications, and confirm wiring and connector locations before replacing parts.
Ideal for technicians and DIY owners, it supports everything from routine service to deeper mechanical and electrical work—including drivability, no-start, warning lights, overheating, brake and suspension issues, HVAC faults, and circuit testing.
Trims covered
- GS Sedan 4-Door
- LS Sedan 4-Door
Engines covered
- 5.0L 302Cu. In. V8 GAS OHV Naturally Aspirated
What’s inside
- Body
- Brakes
- Chassis Electrical
- Driveline
- Engine Cooling
- Engine Electrical
- Engine Mechanical
- Engine Performance & Emission Controls
- Fuel System
- General Information & Identification
- Heating, Ventilation, & Air Conditioning
- Hybrid & Electric Vehicle Systems
- Steering
- Suspension
- Transmission, Clutch, & Transfer Case
- Wiring Diagrams
Why this manual matters
- Faster diagnostics with system-based troubleshooting and wiring diagrams
- Clear procedures and reference sections to reduce guesswork and rework
- Helpful for maintenance planning and verifying parts/specs before repairs
THREADED INFLATOR COMPONENTS MAY HAVE BEEN DAMAGED DURING ASSEMBLY WHICH MAY ALLOW COMPONENTS TO SEPARATE WHEN INFLATOR RECEIVES A SIGNAL TO DEPLOY THE AIR BAG.
INFLATOR COMPONENT SEPARATION ALLOWS HOT COMBUSTION GASES TO ESCAPE INTO THE PASSENGER COMPARTMENT W
REPLACE AIR BAG MODULES CONTAINING POTENTIALLY DEFECTIVE INFLATORS.
TRANSFER SERVICE TIPS FOR THE FRONT WIPER MOTOR MOUNT BRACKET AND DEPRESSED PARK OUTPUT ARM. *TT
THIS ARITLCE IS TO PROVIDE INFORMATION ON REPLACEMENT OF OLD STYLE HOOD LAMP SWITCH TO THE RVISED MECHANICAL HOOD LAMP SWITCH. *TT
SOME VEHICLES MAY EXHIBIT HEATER CORE LEAKS. *SLC
INFORMATION REGARDING TRANSMISSION FLUID USAGE CHARTS. *SLC
THIS INFORMATION IS A SUPPLEMENT TO THE WIPER SYSTEM SERVICE INFORMATION PROVIDED IN THE WORKSHOP MANUALS. THIS SERVICE INFORMATION IS INTENDED AS AN AID TO ASSIST IN DIAGNOSIS AND REPAIR OF ERRATIC WIPER SYSTEM CONDITIONS. *TT
SUBJECT REGARDING CLIMATE CONTROL - EATC - BLOWER MOTOR CONTROL SERVICE TIPS. *JB
SUBJECT REGARDING CONTAMINATION FROM PRIOR TRANSMISSION CONCERNS OR EXCESS WEAR MAY BE TRAPPED IN THE TRANSMISSION FLUID COOLING SYSTEM. *TT
INFORMATION ON THE NEW FLUSH AND FILL TOOL AVAILABLE THROUGH ROTUNDA. *TT
Showing the 8 most recent of 36 technical service bulletins on file with NHTSA.
WHILE DRIVING VEHICLE AT VERY LOW SPEED, VEHICLE WENT OPEN THROTTLE POSITION, IMPACT 12:00 POSITION SPEED UNKNOWN. TT *JB
SUDDEN ACCELRATION, CAUSED LOSS OF CONTROL/ACCIDENT/INJURY. *SKD
WHEN BRAKES APPLIED CAR LURCHED FORWARD. TT
BRAKE FAILURE. *AK
I EMBARKED ON A ROUTINE TRIP TO DINNER IN MY MOTHER'S 1990 MERCURY MARQUIS. I STARTED THE ENGINE WHICH IDLED NORMALLY, AS USUAL. WITH MY FOOT ON THE BRAKE, I ENGAGED THE SHIFT LEVER INTO THE R POSIT
Showing the 5 most serious of 63 complaints filed with NHTSA.
