Went lean...

dano said

Really only a few things can make it read lean. Excess air (vacuum leak), lack of fuel (clogged filter, failing pump, pinched line, etc) or an exhaust leak to throw the reading off, then just a failed sensor.

My question would be where did the breather filter element go that is missing?

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Where did the breather filter go ... now that is a good question. One I've been sweating over. If it got sucked down the carb, well, it didn't do anything detrimental. But because this lean event came on exactly after this event, my mind is stuck on 2 possibilities. 1. It fell out and down on the ground when I pulled the housing off, set it down, and I didn't see it fall out. Or 2. It went down the breather hose. Which it's not really small enough. But like I said, it was kind of crusty the last time I noticed it. Maybe it got worse and broke up, and maybe me picking these parts up lodged it down the tube. But ... would plugging the breather hose lean the AFR? I doubt it, but that's just my assumption, I don't officially know that.

And as far as #1. Maybe it was crusty enough it was blocking up the breather's hose. And when it fell out, now the breather is working correctly. But still, this doesn't seem like it would lean the AFR ... but I don't know that either. Seems like the PCV would pull blowby and air out of the crankcase and into the intake (due to intake vacuum and the PCV valve). Seems like the breather would be allowing some amount of air down into the crankcase when the pcv is drawing it out, creating a balance. In either case, I don't see this affecting AFR that much. But, I could be plain ole wrong.