1999 Mercury Grand Marquis Problems

RepairPal has identified the most common problems with the 1999 Mercury Grand Marquis as reported by actual vehicle owners. We'll tell you what the problem is and what it'll take to fix it.

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Known Problems

The composite (plastic) intake manifold may crack near the thermostat housing and cause a coolant leak. Ford released an updated manifold that was reinforced to prevent a recurrence. No recall was issued for this problem but Ford did extend the warranty to seven years on some models from the date of purchase.

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.

Certain police, fleet, and natural gas models may experience lower ball joint wear, requiring replacement in the front. This was a safety recall.

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.

Transmission problems are common in this model, often as a result of a failed front pump. The pump loses its ability to create hydraulic pressure, which an automatic transmission needs to function. A sign of front pump failure can be a whine type noise.

The engine may overheat at idle when the AC is on. A new, upgraded fan motor and resistor may be required to correct this concern.

Bad spark plugs or an ignition coil can cause ignition misfire, which will illuminate the Check Engine Light.

One or more oxygen sensors may fail resulting in illumination of the Check Engine Light.

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.

The heater hose outlet may leak coolant at the back of the intake manifold. Sometimes this is misdiagnosed as a leaking intake manifold gasket because it resembles a leaking manifold.

An oil leak may develop from the the right side head gasket.  Oil from this type of leak will commonly drip onto the starter. Our technician tell us an updated head gasket is available to correct this concern.