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2001 Ford Excursion PO171 fuel system lean

Tiny
JOE BOCCIO
  • MEMBER
  • 2001 FORD EXCURSION
  • 4 CYL
  • FWD
  • MANUAL
  • 55,000 MILES
What is the posible caused checked vaccum leaks did scan it and found that long term fuel adaptives is plus 25 to lean. Checked exhaust leaks and non found im thinking possile down stream 02 sensor checked timeing its all ok what do you think thanks joe boccio
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Saturday, December 27th, 2008 AT 9:39 AM

1 Reply

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Hello, if scanner shows live engine data, how about freeze frame data and trouble codes if there are any?

As far as the fuel trims, you add short and long together on the same bank, at idle, if it shows +20 or greater, you suspect a vacuum leak. When you raise the rpms to 2500 for just a few short seconds, if the fuel trim reading drops closer to normal by around 15 points, I'm not sure of the exact drop, but closer to normal. Then, again you suspect a vacuum leak. If the readings don't change at all, when you increase the rpms, I don't think it is a vacuum leak.

You may be way ahead of me on this, but, I had to double-check your readings.
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Sunday, January 18th, 2009 AT 3:48 PM

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