Fault code P0300 misfire, P219A Air/Fuel Ratio Imbalance, 2 codes clear at once

[jellyfish1234]

When engine shaking, idle speed not stable, CEL is ON, the cause could be so many. I introduce two situations before, and now I want to talk about when two fault codes occur and clear them at the same time.

The car in this case is Buick GL8 2010, tools is Topdon Artipad. And like before, when we have these two codes, go to live data. Live data is a very accurate way to know which part has issue. Check long term fuel trim bank 1 and bank 2 data, if they are higher than 20%. This Buick--bank 1 is 20.78%, and bank 2 is 13.72%

The reason for bank1 could be various, oil pressure, fuel injector, carbon deposit, vacuum tube, air leak or air flow meter. Check each part from easy operation to hard. Listen if there’s any airflow sound, if so, maybe vacuum tube off

Re-plug the vacuum tube, and scan for fault code again, P219A has gone, only P0300 left. Idle speed is already lower, but engine is still shaking. Check the ignition system, ignition coil, spark plug and related circuit...and then found spark plug burnt,.
After changing spark plug, all is fine now.

[Blue Bowtie]

And this is a perfect reminder to ALWAYS check the basic items as the beginning of any diagnosis.