My 01 Monte Carlo SS has had it's issues and continues to it's issues. It's a lemon but my best friend sold this car to me for a really good price and it already had alot of new parts, suspension, transmission, water pump, etc. I just did a tune-up on and oil change recently. Yesterday I crank it and it sounded like every lifter in the motor was tapping and it was missing real bad and it threw a P0300 multiple random misfire code. I reset the codes and crank it back up and it's been running fine. Thing is I've never heard a motor sound that bad only to recover all by itself just by clearing the codes. Could the random misfire caused all the tapping/ticking sound ? And why would it randomly throw a P0300 and not continue even if I reset the codes

 

Purely speculation, but perhaps it temporarily lost most / all oil pressure for whatever reason, the lifters began to collapse and clatter due to lack of oil pump up, and then the engine began misfiring as the valves weren't opening correctly.

Upon shutting it off and restarting, whatever was plugged / stuck cleared itself, and oil pressure was restored.

Whatever happened has nothing to do with clearing codes. Thats 100% coincidental timing as clearing codes has nothing to do with how the engine runs.