This is the most frustrating problem i have had in a long time. Just before registration and smog renewal was required I was blessed the check engine light. Scanner says 141 and 161. So I figured Id replace the downstream o2's but still have the codes after clearing them. I was just hoping someone has had this problem before; been searching the site for 45 minutes. Thanks in advance. 2000 F-150 with 4.2 manual

 

check for a vacuum leak. Use a can of good carb cleaner (B12 by Berryman is the absolute best) and listen for engine rpms to rise around certain areas. Find where it keeps the rpms higher than another and that is where your vac leak is or should be. It can be a cracked hose, loose bolt (s), manifold, etc. Search and you should find something leaking vac. The MAF can be a source of a lean reading, but usually it is after the MAF that a lean condition occurs. That's a good starting place, good luck.

 

The codes themselves indicate a fault with the sensors themselves I believe. Something with the heater element. I understand the sensors themselves can either indicate a fault or be faulty themselves. I just figured a lean situation would produce a lean code. Worth a shot. Thanks for the reply. Im open to anything.

 

not much help here. lates.