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 Mountaineer owners, lightly cleaned up (personal details are redacted by NHTSA).
Vehicle speed control: while preparing to back up, before shifting, vehicle jumped, and then suddenly accelerated forward, brakes were applied but vehicle wouldn't stop and engine was roaring as if the accelerator was stuck. Vehicle went airborne over an embankment, through a lawn, hit a rock/debris area, tire blew before hitting curve, landed on right rim, was then able to put vehicle in park. Vehicle towed away, dealership currently states nothing is wrong with the vehicle. Help!!
My 2004 Mercury Mountaineer accelerated on it's own as I was pulling into a parking space. The vehicle made a roaring sound. My foot never left the brake pedal and I could not stop it. I jumped the curb, went over a grassy area, over the sidewalk and did not stop until I hit a concrete building at approximately 25-30 miles per hour. It caused significant damage to the building and to the car. Airbag did not deploy. I have had the body damage repaired and my auto insurance has paid over $3,000 for that. My husband took it to our nearest Ford dealer where they ran a diagnostic and it showed an electronic malfunction. They said the throttle body assembly needs replacing. The technician did not give us a print-out and said he couldn't find it when we checked back later. We contacted Ford motor company to see if they would pay for the replacement because our insurance would not. …
Tl* the contact owns a 2004 Mercury Mountaineer. While driving approximately 65 MPH, the contact deactivated the cruise control when the vehicle suddenly stalled. The failure also recurred when driving at slower speeds or when decelerating with the cruise control activated. The vehicle was taken to an independent mechanic for diagnostic testing. The mechanic stated there was a recall and referred the contact to the manufacturer. The manufacturer was made aware of the failure and stated there was a manufacturer's voluntary recall issued but the contact's VIN was not included in the recall. The vehicle was not repaired. The approximate failure mileage was 80,000. Updated 9/21/12 the consumer stated when the failure occurred, there was a total shutdown of the onboard computer, because the power steering and power brakes also failed. …
I had picked up my kids from daycare and I put my vehicle in reverse and backed up. While backing up I heard a loud pop and I got out to see but there was nothing visible. So I put the vehicle in drive and as I was going down the street my vehicle axle broke and my truck hit the street in the middle of traffic. I took it to the Ford dealership and they said it was my axle and my differential had broken also, am I am lucky that I didn't have a bad accident with the extend of the damage of the differential. After I fixed that and it cost $2900. That still did not fix the problem and I had to replace the transfer case. Then all three of my Cadillac converters had to be replaced. I have had problem after problem and oh yeah the back rear gate has been cracked like the month after I bought it.
When using the cruise control the vehicle died: all gauge lights came on (battery, engine, etc.) engine died, no power steering, etc. Had to roll to the side of the road, put vehicle in park or neutral and restart. This problem repeats itself ever time I use the cruise control. And, I see there are other owners of this model that have posted the same complaint. Problem first occurred in January of 2008 however continues today. Fortunately when the engine has died every time I have used the speed control it has not caused an accident.... Yet!
Just purchased a 2004 Mercury Mountaineer today. Driving home, using cruise/speed control at around 30mph and driving on a slight decline, the vehicle shut down. All indicator lights went on, and I had to coast to the side of the road. I put vehicle in park and restarted it without problem. There were no indicator lights (check-engine, etc.) lit up. Immediately went to local Ford dealership and they had no clue, especially since the computer did not have any codes indicating a problem.. I'm canceling the check and returning the vehicle tomorrow.
I drove a 2004 Mercury Mountaineer SUV and as I was turning into the apartment complex from a complete stop, the gas pedal clamped down & I couldn't get the brake to work. My SUV was totaled & I ran into a full-sized pick-up truck, which was totaled too. I reported the problem to the police & my insurance company. The insurance company told me not to tell anyone else about it. It was late evening, so no kids were out, but being unable to control my vehicle, which totaled two full-sized trucks is scary!
When applying the accelerator pedal from a stop position it caused a momentary pulse before the vehicle went into motion. Vehicle had been to the dealer on numerous occasions, and they were unable to locate the problem. The consumer stated that the pause was so severe that it jerks all passengers heads . The vehicle also had transmission problems. The transmission had a harsh shift and clunk when going into reverse or drive. The transmission has been repaired.
While driving 35-45 MPH, car suddenly shut down. Check engine light and battery light came on. Loss of power steering, power brakes, acceleration. Maneuvered vehicle to nearby parking lot, waited, and then restarted the vehicle. No problem in restarting vehicle and all warning lights were off. Used cruise control prior to incident. Intermittent problem; unable to re-create for Ford dealer to diagnose. New battery was installed by Ford dealer in winter 2009.
Tl* the contact owns a 2004 Mercury Mountaineer. The contact stated that while traveling 45 MPH with the cruise control activated the vehicle stalled without warning. The vehicle was taken to a private mechanic where it was found that the cruise control switch needed to be replaced. The vehicle was not repaired. The manufacturer was contacted abut the failure. The failure and current mileage was 138,800. Updated 06/17/14 updated 8/25/2017
Acceleration complaints in other Mountaineer years
Frequently asked questions
How common are acceleration problems on the 2004 Mercury Mountaineer?
NHTSA has 21 complaints about the speed control & acceleration of the 2004 Mercury Mountaineer, 10% of the model year's 210 complaints. The component named most often is cruise control (2 mentions).
Is there a recall for 2004 Mercury Mountaineer acceleration problems?
No. NHTSA lists no speed control & acceleration recall for the 2004 Mercury Mountaineer. 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 Mountaineer acceleration problems start?
Half of the complaints with a recorded mileage happened before about 80,000 miles, and 18% before 25,000 miles.
Is it dangerous?
Owners linked 3 crashes, 0 fires and 3 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.