my 99 Expedition 5.4L eddie bauer was running fine then the idiot light came on when i used the autoxray code reader on it i get lean bank 1/2 both .. I get a slight shudder when i try and takeoff from a stop .. I have searched all vacuum lines no luck all 4 new O2's ... anyone have an idea why i get lean codes and my MPG dropped from 17 to 21 now down to 5 to 8 MPG .. I am to a point of just complete confusion on the thing .. Any help will be greatly appreciated ..

 

Any exhaust leaks before the o2 sensors?

 

no exhaust leaks at all

 

I would double check for vaccum leaks, that's usually the problem when you get the lean codes.

I also gotta say that Bentonville is a beautiful town

 

i have gone through the vacuum system 4 or 5 times now .. and thx , i still have no clues on the problem and the dealership are friggin IDIOTS they say that there is no reason for the lean reading of (LEAN)

 

clean the maf sensor, clear codes, see if it comes back on

 

how are you checking for leaks?? If not, use some carb cleaner on the lines. if you hit one and the engine speed changes, you found your leak

 

The problem usually is the end assembly of the Vacuum which is a 90 degree elbow on the back of the intake. It is a common problem in the 97-03 Ford vehicles as the elbow material isnt strong. I just had the problem at 95,xxx miles. I have pictures of the location if needed, if thats not the problem as stated above the MAF being dirty and blocked may cause it. With the MPG change I would believe it would be a vacuum leak PCV...

 

hey banorcal, can you send or post some pics of where you are talking about please. i am having the same issue and would be interested to find out if you are right. thank you soo much in advance

 

Yes please post the pics I'm having the same issue.