Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2005 Mercury Montego owners, lightly cleaned up (personal details are redacted by NHTSA).
Tl* the contact owns a 2005 Mercury Montego. While attempting to depress the brake pedal, the vehicle began to accelerate and the traction control, check transmission, and failed safe mode warning lights illuminated. Due to the failure, the contact crashed into a bush while attempting to park the vehicle. There were no injuries and a police report was not filed. The failure recurred randomly. The vehicle was taken to several independent mechanics, but the cause of the failure could not be determined. The vehicle was not repaired. The manufacturer was notified. The failure mileage was approximately 270,000.
Tl* the contact owned a 2005 Mercury Montego. While driving approximately 30 MPH, the vehicle experienced unintended acceleration and crashed into the rear of a second vehicle. Prior to the failure, the engine rpms erroneously increased and the vehicle surged forward. The front end of the vehicle sustained severe damage, but the air bags did not deploy. The vehicle was destroyed and towed. There were no injuries and a police report was filed. The manufacturer was notified of the failure. The local dealer was not notified. The failure mileage was 150,000.
When braking it jerks and shifts into neutral and the engine reeves to 5000+ RPM. After braking and slowing it again shifts back into drive. This only happens when braking or increasing speed. No dash lights illuminate, indicating a problem. Having to slow suddenly in traffic is very dangerous. A Ford dealer recommends a new transmission and a transmission shop recommends a new electronic module..this is an intermediate incident problem occurring approximately every two to four weeks. .
Tl* the contact owns a 2005 Mercury Montego. While driving 15 MPH around a corner, the vehicle jerked and the check engine and fail safe mode warning lights illuminated. The vehicle was taken to the dealer where it was diagnosed that the throttle body control unit failed and needed to be replaced. The vehicle was repaired; however, the failure recurred. The manufacturer was notified of the failure. The failure mileage was approximately 150,000.
The car has been lurching forward and decelerating randomly. Keeps going into "failsafe engine mode" and the wrench light comes on but only for a few moments, then runs normally again after restarting. Haven't been able to have the light on long enough to get diagnostics done. Happens while driving or when starting occasionally.
My 2005 Mercury Montego (79,000mi.) has unexpectedly lurched on two occasions. The first time I was driving slowly in a parking lot, and the car suddenly accelerated and lunged forward. Braking helped, but the lunging occurred again each time I tried to drive forward. I was able to move into a parking space and turn the car off which stopped the lurching movement. I sat for several minutes, restarted the car and drove away without incident. This didn't happen again for several months until a similar occurrence yesterday. This time I was ready to back out af a parking space, put the car in reverse and it surged backward. I depressed the brake, put the car in park, and shut it off. Once again I waited several minutes and drove away without incident. This is a very dangerous situation as people could have been close to the car when it lunged, or I could have been in traffic. …
Tl* the contact owns a 2005 Mercury Montego. The contact stated while driving at approximately 65 MPH, the vehicle independently shifted into failsafe engine mode. There was also an unusual increase in engine rpms. The contact shut off the vehicle and when restarting, the warning light was no longer illuminated and the vehicle resumed normal operation. The dealer advised that the failure was potentially caused by debris and should have corrected itself. The contact was advised not to bring the vehicle in. The failure recurred within three days. The vehicle was taken to a local repair facility where the contact was advised that the throttle body was defective and recommended a fuel injection service. The vehicle was taken to the dealer where repairs were made. The manufacturer was not contacted. …
Tl contact owns a 2005 Mercury Montego. She stated that the throttle body failed which made the vehicle shut off in the middle of the highway. She pulled over and turned the engine off and back on then it shut off on its own. The following day the failure recurred and the check engine light illuminated on the instrumental panel. The dealer stated that they would repair the vehicle at the owners expense when the part were available. They later stated that the part was available and that they have exhausted all options to repair the vehicle. The vehicle was not repaired; however, it remained in the dealers possession. The service manager stated that they would not repair the vehicle and the contact should retrieve it. The vehicle identification number was unavailable. The failure and current mileage were 57000.
As I was going down the highway, the car would suddenly feel as though I had put the gas pedal to the floor. It would suddenly accelerate even though I did not change the pressure on the gas pedal. I took the car to the local dealership and they had an owner notification from Ford to clean the throttle body. The work was completed. However, the problem was never fixed. The vehicle would continue to do this on occasion. Now, the vehicle will completely shut off while I am driving down the highway. The fail safe light will come on and I have to coast to the side of the road. I have taken it back to the Ford dealership and another $1,000 later I am having to replace the throttle body.
Tl contact owns a 2005 Mercury Montego. The contact was driving at speeds of 20 MPH. When they attempted to pass another vehicle, she depressed the accelerator and the vehicle was hesitant to increase speed similar to driving while in neutral. In addition, when depressing the brake pedal, the vehicle would jerk abnormally. The dealer reset the vehicle computer system and the vehicle returned to normal operation for a short period; however, the failure recurred. The contact had not taken the vehicle back to the dealer. The failure mileage was 51,000 and the current mileage was 64,000.
NHTSA investigations
Idle instability
On November 29, 2012, Ford Motor Company (Ford) initiated Customer Satisfaction Program 12N03 to extend warranty coverage terms for repair of engine idle RPM surge caused by throttle body deposits in all model year (MY) 2005 through 2007 Ford Freestyle, Five Hundred and Mercury Montego vehicles.The program extends the coverage for up to 10 years of service or 150,000 miles from the warranty start date of the vehicle…
Acceleration complaints in other Montego years
Frequently asked questions
How common are acceleration problems on the 2005 Mercury Montego?
NHTSA has 24 complaints about the speed control & acceleration of the 2005 Mercury Montego, 18% of the model year's 135 complaints.
Is there a recall for 2005 Mercury Montego acceleration problems?
No. NHTSA lists no speed control & acceleration recall for the 2005 Mercury Montego, though it has 2 recalls 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 2005 Mercury Montego acceleration problems start?
Half of the complaints with a recorded mileage happened before about 86,000 miles.
Is it dangerous?
Owners linked 2 crashes, 0 fires and 0 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.