[mrhappy9]

'97 Exp. 5.4 Codes 0171,0174(lean 1&2), 0136,0156(O2sensor 1&2),1131,1151(?). Found loose exhaust connection (pre muffler) which may affect O2 sensors. Have not been able to run drive cycle since clearing codes. Workin on some other stuff while in the shop. Anyone have any experience with this condition? Comments would be appreciated. Thx

[mrhappy9]

update: After drive cycle, chkenglite on, Code 0171,0174 back, others did not return. seems to running ok.

[Canuck623]

On that engine you want to look for rotten rubber hoses that cause vacuum leaks. The most common is the PCV hose. Do a couple of those a week.