03 F150, 6 cyl 4.2

Trying to help my father in law. Seems like it's backfiring when up to speed and putting a load on it. Can feel it in the pedals. Does not do it just revving engine or slow speeds under a load. I haven't gotten the codes pulled yet.

 

backfire or misfire??

 

Backfire. Sounds like a backfire coming out of the manifold. Didn't do it at all today, though. Pulled the codes; O2 sensor, lean bank 1 & 2, and eng exhaust leak.

 

What? Your statements are confusing. And what o2 sensors.