Goes Lean. 1 Bank. No Reason?

sen2two

I've been lubing and pulling it all morning
Jul 18, 2013
396
58
49
So I have the super weird issue, nothing turned up in my searching.

The car starts fine and idles fine. I usually sit and idle for 20 to 30 seconds before I drive off. Somewhere at about 20 or 30 seconds of driving, One bank will go completely lean to where it maxes out the wide band (22.9). While the other bank stays normal. It will stay like that for another 30 seconds or so before the lean bank will go back to normal. It's obvious in how it drives for that time that the wideband is not lying to me.

My wideband is a Innovate DLG-1 dual gauge. 2 sensors just after the long tubes meet the exhaust. I have "true dual" exhaust. So no H or X pipe where the air fuel reading might be mixed up.

What would cause one bank to go lean every day around the same time and about the same amount of time before clearing up... Other than this, the car stays pretty much where it should be at all times.
 
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