This post originally appeared on fordproblems.com
Back in the day, there was a cable connecting the accelerator pedal to the throttle. If that cable snapped, well, you were up a certain creek without a paddle. But at least you knew what it was.
Nowadays every system in your vehicle is controlled by some sort of computer, including the ETB (sometimes called an electronic throttle control (ETC)). The ETB uses data from sensors to control the position of the throttle valve, which in turn manages the amount of air entering the engine.
What is "Limp Home" Mode? ∞
"Limp Home" happens where there's a problem in the logic of a car's computer, such as the ETB.
If the ETB can't figure out what's going on, you can go from cruising down the highway to desperately trying to use what momentum you have left to find a safe place to pull off.
"Limp home" is self-preservation. The vehicle will no longer accelerate above a pre-defined value set by the automaker. The goal is simply to give you the minimal amount you need to find a mechanic.
"I had just started up a long bridge in heavy traffic when the Explorer suddenly lost power, the check engine light and wrench light came on. I was able to drive at very low speed into a lane under construction. I eventually had to be escorted off the bridge at the same low speed by a Port Authority police car."
Mercury owners have reported that throttle body related issues come back with trouble codes P2111 and P2112.
A Parts Delay ∞
ETB problems are very common with Ford and Mercury vehicles and, because of that, the parts are often back-ordered and the average wait time is three weeks.
Because the cars can sometimes come back to life after stopping and starting the engine a few times, mechanics will often send you home and tell you to wait for the replacement ETB to come in. Of course, that means you're at risk of this happening again. In that case, it's worth asking about a rental car.
The Recall That Wasn't ∞
In October 2012, the North Carolina Consumers Council (NCCC) petitioned the government to look into throttle body failures in the 2005-2012 Ford Escape. It was one of the first instances where ETB "limp home" problems were reported.
The petition referenced TSBs Mercury had previously released (TSB 08-18-2 and TSB 09-23-5) that discussed "drive-away hesitation and loss of RPM on deceleration." The TSBs pointed to possible problems in the Powertrain Control Module (PCM) and electronic throttle body (ETB).
The National Highway Traffic Safety Administration (NHTSA) agreed to open an investigation in February 2013. The investigation focused on engines stalling or surging, followed by a sudden loss of power.
The investigation covered the 2009-2010 Ford Escape/Escape Hybrid, 2010-2011 Ford Fusion, 2009-2010 Mercury Mariner/Mariner Hybrid, and the 2010-2011 Mercury Milan.
Ford Motor Company's "Customer Satisfaction" Campaign ∞
During the investigation, Ford found nearly 60,000 warranty claims related to throttle body problems and determined there was an electrical connectivity problem in the ETB.
Ford opened up "customer satisfaction program (13N03)" instead of issuing a recall for those ETB problems. The program extended the ETB warranty up to 10 years / 150,000 miles from the warranty start date of certain vehicles with 2.5L and 3.0L engines.
It was enough to satisfy NHTSA, who closed their investigation. But it did little to satisfy most customers.
Why Didn't NHTSA Recall Mercury's ETB? ∞
An extended warranty is nice and all, but it means consumers have to wait for their ETBs to break before they can get them replaced. That leaves drivers at risk of sudden acceleration or deceleration in dangerous driving scenarios.
NHTSA's role is to "set and enforce safety performance standards for motor vehicles", but in this case they've dropped the ball. Preventive means could have been taken to prevent future incidents with Mercury's defective ETB, but instead we're left with Ford's reactionary program.