2001 Ford Excursion po171 fuel system lean

2001 FORD EXCURSION
55,000 MILES • 4 CYL • FWD • MANUAL
Avatar
JOE BOCCIO
  • MEMBER
  • 1 POST
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
Dec 27, 2008 at 9:39 AM
Advertisement
Avatar
JDL
  • CERTIFIED EXPERT
  • 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.
Jan 18, 2009 at 3:48 PM