2003 expedition, has had catalyst codes for awhile, as well as bank 1 and 2 too lean. Nasty smelling exhaust, jumps while idiling at drive through etc from 500-1000 rpms, gas mileage sucks. Also has humming noise from deep in engine compartment. Shop thinks they found vacuum leak and are replacing purge solenoid, want to make sure this is truely it and im not being taken for a ride, could this really be as simple as that. Thoughts?
been told by several shops need to replace engine, this guy says not the case, quite often mistaken for needing engine replacement