Lean code

[bconnaway]

Originally Posted by JackandJanet

The fact that you're getting it on different tunes suggests a mechanical problem like a leak to me too. But I don't have any suggestions about how to find it. I wonder if there'd be any "blowby" that might create a "soot mark" if there's a leak?

Sometimes you can hear a leak "whistle", but you might need a stethoscope to be able to isolate that from other engine noises.

- Jack

Whenever I let the truck idle, I can hear something sounds like it is rattling (I think that may be the fasteners from the Stage 8 bolts), but nothing like a whistle. So, I cleared the lean code and about a week later it popped up again. But this time it had another one...
P0174: System Too Lean (Bank 2)
P2196: O2 Sensor Signal Biased/Stuck rich - Bank 1/Sensor 1

So, what is going on here? My best guess at this point is an exhaust leak on the gaskets (I had reused the Ford factory ones), causing the system too lean code. Truck tried to compensate and started to actually run rich, causing the driver side O2 to go bad... Just want to get ideas before I go back under and start trying to fix things, not exactly the easiest to change the gasket for the passenger side header.

Also, if it makes a difference, I soldered in my own extensions for the front O2 sensors. I wouldn't say I did a poor job, but it was my first time soldering, so could that possibly be causing these issues?