Did you find anything out?
Sorry I just got here, my shift has been changing back and forth the last couple of days. Today am, tomorrow pm shift. fun stuff. lol.
As far as the Maf, everything starts with the Maf and rpm (which comes from crank sensor). So at certain rpm and loads(load is calculated from Maf) you will get a certain fuel pulsewidth. Then the variables get added, intake air temps, ECT, TPS and others. After all that if the vehicle is in closed loop, then the O2's report back to the PCM and the PCM will adjust short term fuel trim. If STFT stays far from 0% then Long term fuel trims will adjust and make STFT go back to switching around 0%. (normal fuel trims are -5% to +5% with 0 being preferred).
Closed loop can happen before the engine is fully warmed up because of O2 sensor heaters. Sometimes closed loop can be achieved in minutes.
Any misfire can lead to a false lean reading, fuel and oxygen goes into the cylinder and if not burnt fuel and oxygen comes out. The O2 sensors only see oxygen not fuel. So the O2 sensors see all that oxygen that was not burnt in the cylinder and think it was lean, they report to the PCM which adds fuel. That wont fix a misfire so with the introduction to OBD2, the misfire monitor was added to the programming in the PCM. If a misfire is detected, the system will go into open loop and ignore the O2 sensors since they can not be trusted during a misfire.
Hope it is just a spark plug.
Also, I don't recommend driving any custom vehicle until it is finished being tuned. Of course you have to drive it to get datalogs for tuning though.
