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Fuel intake

Tiny
CCOTE08
  • MEMBER
  • 1998 LINCOLN NAVIGATOR
  • 5.4L
  • V8
  • 4WD
  • AUTOMATIC
  • 100,000 MILES
Codes P0171 & P0174
cleaned sensor, fuel pump only 2 yrs old

at very low rpm, it seems to not get enough fuel. It seems it will stall. Does not seem to use more fuel than normal ! Can't seem to find any vacuum leak ?

What next?
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Friday, January 1st, 2016 AT 8:58 AM

4 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Check fuel pressure probably low. Should be 35-45 psi key on or idling auto parts rent gauge
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Friday, January 1st, 2016 AT 9:10 AM
Tiny
WRENCHTECH
  • MECHANIC
  • 20,757 POSTS
On Fords those two codes nearly always end up being a large vacuum leak. The rubber connectors that attach to the intake manifold are a common source. They suck large holes right through the rubber which close up when the engine is shut off. The PCV line is common also. The best way to find them is with a smoke test.
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Friday, January 1st, 2016 AT 2:13 PM
Tiny
CCOTE08
  • MEMBER
  • 2 POSTS
We found a vacuum leak, then still had misses. So did plugs & found a bad one so changed them all. I hope this does it !
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Sunday, January 3rd, 2016 AT 5:13 AM
Tiny
WRENCHTECH
  • MECHANIC
  • 20,757 POSTS
The coils are usually the root cause of the misfires. The plugs may help temporarily but the coil for that cylinder should be changed also.
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Sunday, January 3rd, 2016 AT 5:17 AM

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