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.
1991 Ford Crown Victoria Problem Reports
RepairPal Verified 1991 Ford Crown Victoria Problem Reports
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.
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.
Certain police, fleet, and natural gas models may experience lower ball joint wear, requiring replacement of the front ball joints. Ford has issued a recall on certain vehicles for this condition. Please contact your local dealer for more information.