Which parts fail
Components named in complaints (accelerator pedal, throttle, sudden acceleration, cruise control).
Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2004 Mercury Grand Marquis owners, lightly cleaned up (personal details are redacted by NHTSA).
While driving, I came to a stop light and suddenly, the car idled high and lurched forward while my foot was on the brake, luckily, I was stopped well away from the vehicle in front of me. The car idled high and seemed to have a mind of it's own. I took the back roads home and backed into our garage. The car smelled hot, and I though I had smoked my brakes, trying to keep control of it. Later that night, I told my husband about the car's actions and he did not believe me, though my daughter who was with me at the time confirmed that the car had indeed accelerated on it's own. My husband started the car and it did idle high and get hot once again, although only parked with no one in it. He thought he knew what the problem was and we turned off the car and closed the hood and went inside to order the part. …
My wife was driving our 2004 Mercury Grand Marquis (pre-certified, bought off the showroom floor August 2004); our three teenage foster care children and I were passengers. Our Marquis entered the parking lot of convenience store so that we could install air in left front tire. We did a u-turn in parking lot to proceed to air compressor. With her right foot on brake pedal, my wife steered the car through the u-turn, heading toward air compressor. Suddenly, without any warning, the car accelerated uncontrollably. The brake would not work - brake pedal was pushed all the way down; car continued to accelerate and traveled over a large concrete barrier and crashed into building. The car could not be steered while car sped forward. The air bags did not deploy. We were wearing our seat belts and shoulder harnesses. …
Tl* the contact owns a 2004 Mercury Grand Marquis. While the vehicle was coming to a stop, the contact depressed the brake pedal and the speed and rpms increased without warning. The contact continued to depress the brake pedal; however, the vehicle failed to respond. The contact powered the vehicle off and noticed blue smoke emitting from the rear of the vehicle. The vehicle was taken to the dealer, but the failure was unable to be determined. The vehicle was not repaired. The manufacturer was not made aware of the failure. The approximate failure mileage was 58,000. Ma 09/25 updated 12/05/2017
Dt: while the contact's friend was pulling into a parking lot she pressed on the brake pedal and it hesitated while stopping the vehicle. On a separate occasion, while stopping at a stop light the accelerator pedal got stuck. This caused the contact's vehicle to rear end the vehicle in front. When the brake pedal was pressed the vehicle was non responsive. The contact had to turn the vehicle off to get it to stop. No injuries reported. The vehicle has not been to a dealership to be inspected concerning this problem.
Vehicle headlights work intermittently . Cruse control does not reset or turn on when supposed to. This is also an intermittent problem, sometimes resetting, and sometimes not. Headlights would sometimes not turn on when driving unless pulling turn signal arm toward steering wheel and holding. High beams only would work.
Dt: the vehicel accelerated suddenly and the brakes could not stop it. While in a parking lot to put air in the tires the vehicle just took off and crashed into a building. This happened July 30, 2005 the consumer is getting ready to contact Ford.
When the consumer attempted to come to a stop , the vehicle accelerated into a building. The vehicle was towed. The dealer could not find anything wrong. The consumer found several similar incidents.
Unintended acceleration: last year (feb 2009) my 2004 Mercury Grand Marquis had an unintended acceleration which I (weight lifter) could barely control and I almost crashed into 2-cars. I also had to have the brakes replaced due to severe braking required to stop the car due to the unintended acceleration I used a reliable mechanic (highly rated by the state of ma) as the local Ford dealer shops are over-priced and unreliable. No diagnostic codes showed-up at the shop after the problem, but I would not have my wife drive this car? The car is well maintained and I had a previous Grand Marquis, so I know the car better than most. Have you heard about this problem and is there a recall? Ford was contacted on feb 23 2010, via their protal, and indicated that there was no problem or recall, and suggested that I go to their dealer (did not go as I have no need for bs). …
Tl* the contact owns a 2004 Mercury Grand Marquis. While driving approximately 65 MPH, the vehicles speed increased. When the brake pedal was engaged, the vehicle began to reduce speed. The contact maneuvered onto the emergency lane and turned the vehicle off. After restarting the vehicle, it began to function normally. The failure occurred three times. The vehicle was taken to an authorized dealer for diagnostic testing and the they were unable to diagnose the failure. The manufacturer was not made aware of the defect. The approximate failure mileage was 50,000. The VIN was unavailable.
Dt*: the contact stated while approaching a stop under normal braking, the vehicles engine revs and surges forward. The brake pedal must be depressed to the floor to stop the vehicle. This happened 5 times and the vehicle was inspected by the dealer however; the problem could not be duplicated. The vehicle was driven over 6,000 miles when the problem returned. It was taken back to the dealer for service and again the dealer was unable to duplicate the problem. The consumer believed there is a problem with the transmission. Updated 04/06/06.
Acceleration complaints in other Grand Marquis years
Frequently asked questions
How common are acceleration problems on the 2004 Mercury Grand Marquis?
NHTSA has 23 complaints about the speed control & acceleration of the 2004 Mercury Grand Marquis, 7% of the model year's 348 complaints. The component named most often is accelerator pedal (4 mentions).
Is there a recall for 2004 Mercury Grand Marquis acceleration problems?
No. NHTSA lists no speed control & acceleration recall for the 2004 Mercury Grand Marquis, though it has 1 recall for other components. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 2004 Mercury Grand Marquis acceleration problems start?
Half of the complaints with a recorded mileage happened before about 50,000 miles, and 21% before 25,000 miles.
Is it dangerous?
Owners linked 5 crashes, 1 fire and 2 injuries to speed control & acceleration problems on this model year. If you notice symptoms, have the car checked before driving further.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.