Quick question y'all

​​​​​On cold starts, and when the oil is reaching operating temperature the car starts sputtering alot.

I checked my logs and there are occasional lean spots 15.1-15.5 however after I reach operating temp and hit boost a few times the logs show 14.3-14.8 afr under cruising conditions (20 mph to 60 mph).

In other words, can fouled plugs (copper ngk one step colder gapped to 0.03) cause this sputtering (did maybe 10k miles however alot of those miles I was still setting up the tune)? Or maybe I have oil in the plug well and have an artificial misfire when trying to reach operating temp (which the ECU didn't pick up yet)?

Can a misfire in one cylineee theoretically cause afr to jump into lean condition?

Thank you
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Yes, a misfire will lean out.
I would replace the plugs since they are very cheap and especially since they have had the abuse of the tuning.(I'm using 2 step colder NGK V-power coppers on whatever gap they came in the box with)
You can always take one out and look at it

 

15.5 doesn't seem like a huge discrepancy (roughly 5%) especially at start-up where other compensation maps are influencing the AFRs ... I'd inspect the plugs before concluding that it's a fouled plug, revisit your applicable compensation tables and go from there.

 

I can idle smoothly no problem at 16 or 16.5. I don't think 15 or 15.5 afr has anything to do with the sputtering. If a plug doesn't fire properly, you will have unburnt fuel in the cylinder make its way to the O2 sensor, which will read rich, not lean. Widebands read slowly, so you can't really depend on them for fast, transient events. I suspect a vacuum leak more likely than a plug issue...

 

A misfire reads LEAN. Oxygen sensors do not detect fuel, they detect OXYGEN.