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.

RepairPal Verified
Average mileage: 170,787 (110,000–235,675)
Exhaust & Emissions affected: 2.0L 4 Cylinder
2 model years affected: 1999, 2000
11 people reported this problem
4 people shared problem details
1999 Mercury Mystique130,000
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 Mystique110,000
stalling, rough/erattic idel cleaned iac valve with carb cleaner
how will i know when the time belt is off or broken also what are the sounds that i would hear because when try to crank the car it makes a spudder sond and wont turn over
2000 Mercury Mystique235,675
Idles rough, doesn't stall ,just rough idle
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