My 96 F150 5.8 keeps giving me a CEL with bank 1 or 2 lean codes,sometimes both codes if I leave it long enough. It has been doing this for about 6 months and is worse when it is above 40 degrees. I have changed the fuel filter,cleaned the MAF,PCV and inspected vacume lines with no luck. What else could I try? It seems to run fine otherwise,but I would rather not be letting it run lean. Thanks

 

I would start by checking the fuel pressure.

 

how many miles are on the O2 sensor(s)?

 

It's doubtfull both O2 sensors have gone bad at the same time, so this is more likely to be related to the thermactor(air injection) or EGR system, look for leaks in the plumbing for the air injection particularly in the tube across the back of the motor that's nearly impossible to see.