1999 Mercury Mystique Repair and Maintenance
A guide to problems, costs, maintenance and repair for your 1999 Mercury Mystique
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1999 Mercury Mystique ProblemsCheck Engine Light Due to Plugged EGR Passage
The Check Engine Light can illuminate with codes due to the lack of EGR (exhaust gas recirculation) flow caused. This is commonly a result of a clogged passage in the intake manifold. To correct this problem, the EGR valve has to be removed and the passage cleaned thoroughly. Partial restriction of this passage can cause smog test failures for the NOx emissions without causing a drivability symptom.
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.