One problem related to engine knocking noise has been reported for the 2005 Mercury Grand Marquis. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2005 Mercury Grand Marquis based on all problems reported for the 2005 Grand Marquis.
Knocking noise from engine/transmission area when car is stopped at idle, transmission in gear, windows closed and heater fan off. Problem: intermittent, erratic, muffled knocking noise. Heard from inside the car.