Problems for specific Mercury Grand Marquis years:
Problem with your car? See what our experts say or submit your own.
1991 Mercury Grand Marquis Problems
The throttle position sensor (TPS) may fail. Common symptoms of a defective TPS can be rough idle, hard starting, hesitation on acceleration, poor fuel economy, and stalling.
A spring in the seat belt buckle may wear or fail, causing the airbag light on the instrument panel to illuminate. Failed buckles will require replacement.
If you experience difficulty starting the engine when cold, stalling at idle, or hesitations during acceleration, it may be the idle air bypass valve. This valve helps the vehicle idle steady when the accelerator pedal is not pressed.
I changed the thermostat and installed it correctly but usually my Grand Marquis puts out hardly any heat at all.
It is not uncommon for the intake manifold and/or valve cover gaskets to develop a coolant or oil leak. Leakage from the intake manifold may result in coolant in the engine oil. Coolant mixing with the engine oil severally impacts the lubrication ability of the oil. Internal engine may result if this condition is not repaired promptly.