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1990 Mercury Grand Marquis Problems

RepairPal has identified the most common problems with the 1990 Mercury Grand Marquis based on complaints from actual vehicle owners. We'll tell you what the problem is and what it'll take to fix it.

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6
Known Problems

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.

The EGR valve position (EVP) sensor can fail on this vehicle. The EVP sensor measures the EGR valve position and transmits the date to the engine control computer. If it fails, drivability and fuel economy can suffer, the Check Engine Light will commonly illuminate.

The battery light may illuminate on the instrument panel because the alternator wire harness connector is damaged. A new connector kit is available and should be installed to correct this concern.

Wear on the rear axle shafts near the bearings can create excessive play and lead to gear oil leaking past the seals. Gear oil will leak onto the brake backing plate, brakes, and wheels.

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.

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.