1999 Ford F250 diagnostic codes - "system lean"

1999 FORD F-250
147,000 MILES • V8 • 4WD • AUTOMATIC
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DUKELOWELL
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I have a 1999 F250 that I've had for a little over a year. Runs great, no complaints. Yesterday my "service engine soon" light came on. Took it in for service and they read the codes (PO171 & PO174) which indicate system lean left bank and system lean right bank. How do I fix this?
Sep 3, 2010 at 6:17 PM
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RASMATAZ
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Lean fuel condition could be caused by one of the following below:

1.Vacuum leaks
2.EGR and PCV valve.
3.Low fuel pressure.
4.Dirty fuel injectors.
5.Mass Air Flow Sensor.
6.Oxygen Sensor.
Sep 4, 2010 at 2:56 PM