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1997 Ford Explorer runs lean

Tiny
ERNEST8FINGERS
  • MEMBER
  • 1997 FORD EXPLORER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 170,000 MILES
My 97 Ford Explorer has the "check Engine" light on and I read the trouble codes- P0133/P0171/P0174 this is telling me that the "upstream O2 sensor(133) is malfunctioning and both banks of engine are running lean(171 & 174 both pending). Should I start with replacing O2 sensor? After clearing these 3 codes(w/o fix) I immediately get 2 codes(171 &174) w/o the O2 sensor(that takes another 40+ miles to show up). I hate these electric fuel pumps buried in the gas tank. I am starting to think its the fuel pump or maybe the fuel filter? Thanks in advance-Ernest
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Friday, March 12th, 2010 AT 3:57 PM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,700 POSTS
It could be the sensors, but before replacing them, I would look for vacuum leaks. Many times a leak will cause a lean mixture.

Let me know what you find.

Joe

PS: If you are worried about the fuel pump or filter, check pressure at the fuel rail.
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Saturday, March 13th, 2010 AT 12:18 PM
Tiny
ERNEST8FINGERS
  • MEMBER
  • 2 POSTS
It could be something as simple as a bad gas cap. I replaced the cap-cleared the codes and so far(maybe 100 miles) no light. Of course with 170000 miles it- just a matter of time before that "damm" light comes back on. I am poor and will run this truck(which has been a solid performer) till the flames force me out-lol. Thanks for the reply and advice.
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Saturday, March 13th, 2010 AT 1:05 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,700 POSTS
Let me know if it worked.
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Saturday, March 13th, 2010 AT 5:27 PM

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