Engine Stalling and/or Hesitation on Acceleration due to Faulty Idle Air Bypass Valve on Mercury Mystique

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.

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Average mileage: 169,960 (110,000–235,675)
Exhaust & Emissions affected: 2.0L 4 Cylinder
2 model years affected: 1999, 2000
11 people reported this problem
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Viewing 1 - 4 of 4 problem details
1999 Mercury Mystique 130,000 mi,
I'm having problems with starting car in mornings. The car will crank but not turn over. I've brought the car to 2 different mechanics after repairs were made w/ new fuel pump, radiator fluid changed, new sensors, and finally a replaced air control valve. After the new valve the car ran fine for 3 days, and then the problem started all over again. The car runs fine & restarts great after it is warmed up. But, the mornings it will not start. I'm about ready to give up!
2000 Mercury Mystique 110,000 mi,
stalling, rough/erattic idel cleaned iac valve with carb cleaner
2000 Mercury Mystique 165,000 mi,
My car starts rough then idles down until it shuts off.
2000 Mercury Mystique 235,675 mi,
Idles rough, doesn't stall ,just rough idle