Hello, I'm Chris, a current Ford Lincoln Mercury employee.
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Your vehicle uses an electronic throttle body, so there is no cable running from the throttle to the accelerator pedal. Even though this is not recommend, it is a cheaper try. Remove the air intake system to gain access to the throttle body. Turn the key to run with the truck off. Have someone hold the throttle open full by way of the accelerator pedal. Now use a carb cleaner spray and a tooth brush and clean the throttle body bore and plate and plate edges very well. Now remove the negative battery cable for 30 minutes to clear all codes and prior strategies. Now reassemble and give it a shot. If this fails then you are going to need to replace the complete throttle body. The likley cause here is carbon and oil deposits have caused the plate to stick and caused the motor to ETB motor to fail or go to failsafe since it could not move it.