Possible causes
– Intake air leaks
– Faulty front heated oxygen sensor
– Ignition misfiring
– Faulty fuel injectors
– Exhaust gas leaks
– Incorrect fuel pressure
– Lack of fuel
– Faulty Mass Air Flow (MAF) sensor
– Incorrect Positive Crankcase Ventilation (PCV) hose connection
– Faulty front heated oxygen sensor
– Ignition misfiring
– Faulty fuel injectors
– Exhaust gas leaks
– Incorrect fuel pressure
– Lack of fuel
– Faulty Mass Air Flow (MAF) sensor
– Incorrect Positive Crankcase Ventilation (PCV) hose connection
Tech notes
The P0171 is a very common code for the 1999 Ford Windstar, the Intake Plenum Gasket ans seals needs to be replaced. Here a link to a web site with information how to repair:
1999-2003 Fords Windstar Code P0171
When is the code detected?
– Fuel injection system does not operate properly.
– The amount of mixture ratio compensation is too small. (The mixture ratio is too lean.)
– The amount of mixture ratio compensation is too small. (The mixture ratio is too lean.)
Symptoms
– Engine Light ON (or Service Engine Soon Warning Light)
– Excessive Fuel Consumption
– Excessive Fuel Consumption
P0171 1999 FORD WINDSTAR Description
With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the theoretical mixture ratio based on the mixture ratio feedback signal from the heated oxygen sensors 1. The Engine Control Module (ECM) calculates the necessary compensation to correct the offset between the actual and the theoretical ratios.
In case the amount of the compensation value is extremely large (The actual mixture ratio is too lean.), the ECM judges the condition as the fuel injection system malfunction and light up the Malfunction Indicator Light (MIL) (2 trip detection logic).
In case the amount of the compensation value is extremely large (The actual mixture ratio is too lean.), the ECM judges the condition as the fuel injection system malfunction and light up the Malfunction Indicator Light (MIL) (2 trip detection logic).