Mike's Workshop Manuals
: Service manuals for every vehicle
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Ford
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1990
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Taurus GL, 4D Sedan, 2.5 D
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Repair and Diagnosis
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Engine Performance
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System
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Engine Controls - Tests W/Codes - 2.5L
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Test H - Fuel Control
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Code 86
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Codes 41 and 42
Codes 41 and 42
Intermittent HEGO circuit (SIG or GND circuit).
Sticking VAF meter air vane (flapper door), due to contamination.
Contaminated HEGO sensor, lead or silicone fouled.