How lean is too lean
 

I havent recieved any codes for it yet so it must not be terrible, but at start the short term fuel trims are 0 adjustment and the longterm are about 7% lean. As the truck is warming up the short terms go all the way to 11% lean for awhile before going to 7% lean when warm. My fuel does have 10% ethanol now which it never had in the past. Before I did my tuneup months back I was anywhere from 5 to 10% rich.

RE: How lean is too lean
 

If it runs right, I would not worry about it. STFT will fluctuate all over the place. If you were getting upwards of 20% lean LTFT, then I would suspect a fuel leak internal to the plenum. If it were 20% rich, I would suspect a vacuum leak.

RE: How lean is too lean
 

Oh ok if it gets to like 20 for long terms I will post again for fixes.