One problem related to engine has been reported for the 2005 Mercury Montego. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2005 Mercury Montego based on all problems reported for the 2005 Montego.
While idling when stopped or when moving slowly, the engine speed suddenly accelerates to above 3500 rpm causing the car to lurch forward unless the brake is firmly applied. The sudden acceleration lasts 3 to 5 seconds. Placing the gear into neutral has no effect on the engine speed. This happens sporadically. In the last 3 months it has happened approximately 7 times. Dealer says the car's computer system reports nothing unusual.