Spark Plugs and Coils
 

I was having an O2 sensor code for downstream. I had recently completed testing of the coils and replaced all plugs with recommended copper core. If I cleared the code and immediately ran on the interstate, the code would not appear. It only showed up on in-town driving on bank 1. Tried switching coils from side to side and the code would not change sides. Went ahead and bought new coils even though they tested ok and had no visible cracking or damage. Pulled the plugs and none of them showed abnormal sparking or oil. Replaced the coils with the newer style longer torx bolt BERU version and wanted to try Ruthenium plugs just because. Started it up and the engine is running smoother and feels stronger when revving up through 6,000 rpm's. No O2 code return throughout in-town or highway driving. Not sure exactly what eliminated the problem, but I do recommend Ruthenium plugs or would suggest them to those who have nothing better to do with their money. :)