Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2009 Mercury Mariner owners, lightly cleaned up (personal details are redacted by NHTSA).
Tl* the contact owns a 2009 Mercury Mariner. The contact stated that while driving approximately 25 MPH, the vehicle hesitated and lunged forward as the engine warning indicator illuminated. The contact powered the vehicle off and back on and drove the vehicle without incident, however, the failure recurred approximately two weeks later. The contact powered the vehicle off and back on, however, the vehicle failed to accelerate. The vehicle was towed to an independent mechanic and was diagnosed that the throttle actuator needed to be replaced. The vehicle was repaired. The manufacturer was not made aware of the failure. The approximate failure mileage was 89,000.
Tl* the contact owns a 2009 Mercury Mariner. The contact was entering a parking space when the vehicle exhibited an abnormally loud revving sound and accelerated into a fence without warning. There were no injuries nor was a police report filed. The contact was able to secure an appointment to have a diagnostic performed on the failure. The manufacturer was notified of the failure but the vehicle was not repaired. The failure mileage was 26,006 and the current mileage was 26,011. Updated 02/09/12 the consumer stated the body damage was repaired. However, the vehicle continues to accelerate. Updated 02/13/12
I am getting continual throttle body errors on my 2009 Mariner. It goes into low power mode so I can "limp home". It happens mostly on highways when I need to "punch it" and get alot of acceleration.
The PCM shorts out and fails when sparkplug and Coil packs replaced this cause the steering system to fail speedometer to quit and no transmission connection
Was driving down country road and all of a sudden felt then engine what I thought was kick out of gear. Had no acceleration at all. Pulled off road and the vehicle was running in a rough idle, but still could not give it gas. Once placed in park the idle leveled out and still no acceleration. The wrench symbol was on. I stopped the engine and waited 10 minutes then restarted engine and everything was OK. For about 3 months. I took into the Ford dealer only to be told there was no code and they could do nothing without it. Problem has gotten steadily worst. And now it is at point where wife can not drive her car! I am driving it and finally yesterday the engine light came on. I ran it to autozone where they confirmed the dreaded p2112 code. I took it to the Ford dealer today figuring alright less than 5 years old and 42,000 miles I would finally get it fixed. No go! …
While driving on the taconic state parkway, traveling at approx. 55 MPH, the engine failed to respond to the throttle and while the car was still in gear, the vehicle merely began coasting. I safely steered the car to the shoulder of the road, and turned the vehicle off. After approximately 2 minutes, I was able to re-start the car (with some hesitation). I then turned around to attempt to drive home. The same situation occurred one more time while traveling home (approx. 30 miles). I brought the car to metric motors of lake carmel, ny. Their computer diagnostics identified the problem as the throttle actuator control. They said that they unstuck the part (cost to diagnose & make repairs $422+) and I again began driving the car. Unfortunately, after visiting nyc on Saturday, October 19, 2013, the same problem occurred, again while driving home on the taconic state parkway. …
I was on a high traffic freeway coming home from a maternity appointment (I was 7months pregnant and it was hot) and going 70mph middle lane. When my car just cut off. I was still moving but my dash was off check engine light came on and I pulled to the side. I could get it started back up but it went off again. I finally got off on a ramp. I had to have my car towed and rent a car. Between the tow rental and work on my car the total was (est 1400). Then a year later it began every now and then stalling or surging while I was driving. It has progressively worsen. Now it has been when I stop or let off the gas it goes dead. Recently went to an auto shop and they hooked it to the computer. It said it was my throttle body. It was cleaned and all was fine for a week. And now it is doing it again. I finally did google throttle body and Mercury Mariner.I found other complaints.
Driving home from work the car went into "limp mode", pulled over to side of road, called for tow and had car taken to shop for diagnostics and repair. Shop determined it was faulty throttle body ( there were over 700,000 orders for replacements on website at this time)part was on backorder---came in, was replaced and I paid the bill of $720.60 for parts, labor, towing and taxes. I got letter from Ford that part is now a recall item so I take the bill to kerry Ford in cincinnati, oh and they take all of my info and send me a check for $167.85 and tell me too bad for not having work done at Ford store, that's all I am going to get. This does not even cover the cost of the part alone. So as a stranded motorist, I was supposed to think of a Ford dealership first instead of safety first and getting my car repaired.
2009 Mercury Mariner. The rear end of the vehicle makes a squealing noise upon acceleration I took the car back to the Ford dealership in hillsdale. The vehicle was in the shop 12/9/2009 through 12/16/2009. Unable to fix the noise, Ford motor company had them tear down the transmission and replace the drive chain. When I picked up the car I was told that the noise was still there and that Ford engineering said it should not be a problem. The noise was still consistent and has grown increasingly louder. Since this initial complaint I have received a recall notice for the transmission solenoid regulator valve. The vehicle has been accelerating when it shouldn't and not accelerating when it should, like when merging into traffic when the transmission would not perform properly.
This is the fourth time since purchasing the car at carmax in October 2012 that the car has "shut off" without warning at low speed when close to parking or driving slow--without rhyme nor reason--I had it diagnosed at carmax to no avail, then cherokee Ford to no avail (where I purchased a new battery), then at christian brothers auto where they replaced the spark plugs and coil.( I have an extended warranty so my cost was 200dollars) the problem continues. I have done research and see the throttle body is most likely the culprit and a safety alert is on the web from consumer report and Ford forum and north carolina safety board---I am having the trottle body replaced at my expense--my daughter drives this vehicle and I want it safe! Apparently this involves this model 2009-2012.
Acceleration complaints in other Mariner years
Frequently asked questions
How common are acceleration problems on the 2009 Mercury Mariner?
NHTSA has 41 complaints about the speed control & acceleration of the 2009 Mercury Mariner, 13% of the model year's 315 complaints.
Is there a recall for 2009 Mercury Mariner acceleration problems?
No. NHTSA lists no speed control & acceleration recall for the 2009 Mercury Mariner, 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 2009 Mercury Mariner acceleration problems start?
Half of the complaints with a recorded mileage happened before about 70,000 miles, and 3% before 25,000 miles.
Is it dangerous?
Owners linked 1 crash, 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.