Last night i was driving and all of a sudden i heard this vibrating noise. It turnned out to be a insulator of my exhaust manifold maybe. I cant see whats underneath it. My O2 sensor is in it so i can partially see under it. LAst night when i stopped it was dark. A buddy rev'd it and i saw a blue flame/spark. I thought it was the o2 sensor. Now my car will start up but run rough and dies. I dunno if its the o2 sensor or what. There is a line right next to the insulator and i think i may have a vacum leak. IM gonna check right now. What are some of the things it would be down there if its not a vacum leak. WHat are the chances it an o2 sensor. Its a non-turbo and i thought only turbos have they're o2 sensors on the exhaust manifold. I think it might be my pre-silencer or pre-cat maybe.

 

i cant find any leaks. I disconected my O2 sensor and it runs the same? that mean it ****?