2004 Ford Freestar System Too lean (P0170, P0174 codes)

2004 FORD FREESTAR
66,000 MILES • 6 CYL • FWD • AUTOMATIC
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REVROADRNR
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My computer is showing system too lean. I ran a systems check for all oxygen sensors, and the egr valve. All checks OK. I reset the computer and the check egine light is off. What could have caused this light to come on and show this code. If it matters, the van was taken out into a snowstorm the night before.
Dec 16, 2007 at 4:47 PM
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AACPLUS
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That senario is eerily similiar to a problem that plagued the older Freestars....I mean the Windstar...
It would be sad if the O2 sensors were dying at 66K. Or that a computer or EEPROM had problems.

Seriously, If it is intermittent, I would check for vacuum leakage at the intake gaskets, EGR passages for carbon buildup causing blockage, Possibly an intermittent voltage drop at a harness/component connector, but without checking TSB's or Recall info, I would hope those things, or intake gasket/valve cover design and related problems are not found to be the cause.
Maybe you will find that it was just a one time fluke or "glitch" and will not re-occur.
I will research this symptom and reply with any additional information I find of value.
Mar 17, 2008 at 2:13 PM