1990 Mercury Grand Marquis Repair and Maintenance
A guide to problems, costs, maintenance and repair for your 1990 Mercury Grand Marquis
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1990 Mercury Grand Marquis ProblemsEVP Sensor Failure May Cause Drivability/Fuel Economy Issues
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 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.
1990 Mercury Grand Marquis Questionscar starts without ignition on solenoid wiring diagram solenoid on fender (1 answer)
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