The good news is that testing a misfire code, or misfire codes, or a rough idle condition is not that hard and it's something you can do! In this tutorial, I'm going to explain in some detail the most common causes of misfires and misfire codes (P0300, P0301, P0302, P0303, P0304 -OBD II equipped 1.8L Toyota).
Solder flux is a type of metallurgy component used when soldering two metals together. The flux is an inert substance that prevents the formation of metal oxides at extreme temperatures.
1 Solder can contain a flux core of natural rosin (tree sap) or a chemical acid. The metal of the solder encircles the core, like a tube.  The purpose of the core is to serve as a flux, or purifying agent. The flux prevents oxidation in the solder as it cools, keeping it strong and pure.