One problem related to engine belts and pulleys has been reported for the 2011 Ford Flex. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2011 Ford Flex based on all problems reported for the 2011 Flex.
Upon acceleration, usually from a complete stop such as accelerating from a stop sign or on a green light, it feels as though the gears do no catch & the car jerks and the rpm's raise but the car stops accelerating. Will also have a "stuttering" or "jerking" while at a complete stop with break pedal being pressed down. I have taken this issue to the dealership as it is still under extended warranty and have been told that everything checked out normal & the mechanic at the dealership was unable to get the vehicle to have such described malfunctions because it is doesn't happen every single time the car is driven. The jerking while driving actually occurs on a daily basis but is sporadic & can jerk you forward due to the sudden loss of acceleration capability, startling and painful because the seatbelt mechanism has engaged in the past.