[davindersangha]

Had a Mini R56 for a year now and recently upgraded it's catalytic convertor due to an MOT fail. However, since then it juddered and struggled to gain speed for a moment, before being okay. The engine light flashed sometimes and the P0420 error showed as a cat convertor issue.

However, I recently filled it to the top with Super Unleaded and it seems to have cleared the speed issue. Is this because the converter is new and it needs a higher octane fuel?

 

[Denys Milano]

Could be due to the bad connector of the O2 sensor, or not good new cat, try connection odb2 reader and see live data of the oxygen sensor 1 and 2