1984 Mercury Grand Marquis: common problems

Owners of the 1984 Mercury Grand Marquis filed 15 complaints with NHTSA, most often about electrical system and engine and cooling. Details by component below, with sources.

Key figures

Owner complaints: 15
involving a crash: 2

What fails most often

1 Electrical system 33% of all complaints
2 Engine and cooling 33% of all complaints
3 Vehicle speed control 27% of all complaints
4 Fuel system 13% of all complaints
5 Structure 13% of all complaints
6 Suspension 7% of all complaints

Circle size and colour show each component’s share of NHTSA complaints. Schematic only, not a drawing of the exact model.

Electrical system: 5 complaints (33% of all).
Engine and cooling: 5 complaints (33% of all).
Vehicle speed control: 4 complaints (27% of all), 2 of them with a crash reported by the owner.
Fuel system: 2 complaints (13% of all).
Structure: 2 complaints (13% of all).

Engines and transmissions

US-market versions per EPA. On the right: how many NHTSA complaints name this engine or transmission type.

5 L · petrol · 8 cyl
automatic, 4-speed

Symptoms owners describe

How many of the 15 NHTSA complaints mention each symptom (automatic count from complaint text; one complaint can mention several).

stalls while driving5 · 33%
smoke, burning smell, fire3 · 20%
engine failure or replacement1 · 7%
hesitation when accelerating1 · 7%
won't start1 · 7%
unintended acceleration1 · 7%

Components owners complain about

Component	Owner complaints	involving a crash
Electrical system	5	0
Engine and cooling	5	0
Vehicle speed control	4	2
Fuel system	2	0
Structure	2	0
Suspension	1	0
Other	2	0

What owners report

Short excerpts of NHTSA complaints in the original wording. These are owner statements not verified by NHTSA; personal data removed.

Consumer had the vehicle in park, then put the vehicle in drive, and the vehicle just took off, causing the consumer to run in a yard and went down an enbankment and hit a tree. The insurance company claim that the throttle got stuck.
Vehicle speed control · crash · 1998-10-19 · NHTSA complaint #829142
Accelerator stuck while attempting to back up, causing sudden acceleration/loss of control/accident.
Vehicle speed control · crash · 1995-04-27 · NHTSA complaint #481258
Engine will idle very high at stops and will stall when turning.
Engine and cooling · 2001-01-23 · NHTSA complaint #558010
The car constantly stalls upon turning, deceleration, and braking, causing near traffic accidents. Car was check over for malfunction, but to no avail.the rear of the car is sagging very badly, causing me to have to replace the rear bumper and tailpipe. The height of the car from ground to frame is approx.
Fuel system · 1998-11-11 · NHTSA complaint #700505
When coming to a stop the brake pedal and the accelerator have to be depressed to keep the vehicle from stalling.
Engine and cooling · 1998-03-04 · NHTSA complaint #821810
While driving vehicle on wet slushy type pavement owner took foot of accelerator and engine continued to rev. Cause has not been determined.
Vehicle speed control · 1997-12-29 · NHTSA complaint #820135
Engine failed to start after vehicle parked overnight, cause unknown, not checked by dealer, sears checked battery/alternator, no problem. Vehicle available for inspection.
Electrical system · 1997-09-16 · NHTSA complaint #816383
Evp sensor core system failed, keeping egr valve open, causing engine to stall. (first vehicle on 601573)
Engine and cooling · 1996-09-23 · NHTSA complaint #502774

When owners complained

NHTSA complaints by filing year. The peak shows at what age the problems show up most.

19952
19966
19972
19983
19991
20011

Comparison

By complaint count this model year ranks 9,286 of 36,656 model years in the NHTSA data (top 25% most complained about).

On average one model year of the Grand Marquis has 117 complaints (34 years in the data). This year has 15, below average.

What to check before buying

Electrical system. Scan all modules, test the battery and alternator, inspect connectors near the impact zone.
Engine and cooling. Radiator and fan after a frontal hit, coolant level and condition, overheating.
Vehicle speed control. Accelerator pedal, cruise control, throttle codes.
Fuel system. Fuel smell, leaks, rough running, fuel-system codes.

Other years of this model

Questions and answers

What are the most common problems with the 1984 Mercury Grand Marquis?

Owner complaints to NHTSA most often mention: electrical system, engine and cooling, vehicle speed control. Total complaints: 15. The most frequent symptoms in complaint texts: stalls while driving (33%), smoke, burning smell, fire (20%), engine failure or replacement (7%).

How many service bulletins (TSB) were issued for the 1984 Mercury Grand Marquis?

NHTSA lists 0 manufacturer service bulletins for this year. A bulletin tells dealers how to diagnose or fix a known issue; it is not a recall.

Should I buy a 1984 Mercury Grand Marquis from a US auction?

Owner complaints describe defects, not crash damage. Before bidding, check the components listed above and review the lot photos: VinWind builds a report of visible and hidden damage by VIN.

Other 1984 models

Read also

Sources: public NHTSA data (USA): service bulletins and owner complaints; YouTube: links to videos credited to their authors. Complaints are owner statements not verified by NHTSA, and describe defects rather than crash damage. Data updated 2026-11-05.