1998 Ford Expedition OBD codes 171 and 174

Tiny
ENG961
  • MEMBER
  • 1998 FORD EXPEDITION
  • V8
  • 2WD
  • AUTOMATIC
  • 135,000 MILES
How do I find the problem and the vaccum diagram
Monday, July 19th, 2010 AT 9:48 PM

4 Replies

Tiny
MHPAUTOS
  • MECHANIC
  • 31,937 POSTS
Hi there,

Thank you for the donation.

These codes indicate lean mixture for both banks, so the first thing I would be looking at is the inlet manifold, I think we may be looking for something that is affecting both banks at the same time, a small vacuum hose off will not do this.

Mark (mhpautos)
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Monday, July 19th, 2010 AT 10:00 PM
Tiny
ENG961
  • MEMBER
  • 16 POSTS
Like what
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Monday, July 19th, 2010 AT 10:13 PM
Tiny
ENG961
  • MEMBER
  • 16 POSTS
What am I looking for
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Monday, July 19th, 2010 AT 10:20 PM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Lean fuel condition can be caused by the following.

1. Vacuum leaks
2. EGR and PCV valve.
3. Low fuel pressure.
4. Dirty fuel injectors.
5. Mass Air Flow Sensor.
6. Oxygen sensor

Clean the MAF sensor and test the EGR-DPFE sensor
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Monday, July 19th, 2010 AT 10:26 PM

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