Engine misses intermittently after reaching operating temperature.

They are located in the exhaust system. You have to be careful about replacing parts without a proper diagnosis, you will likely replace good parts and still have the same problem, and you may even introduce new problems. If you can post the codes you read out, then I can give you some more info about what approach you should take to fix this issue.

I used a scanner to find out what caused the check engine light to come. the read out on the scanner said oxygen sensor failed on first sensor first bank . Could you tell or e-mail a diagram giving the sensor locations.