2002 Nissan Altima "mileage change spark plugs 2011" Questions

change the misfires. Haven't replaced the oxygen sensor or EGR sensor yet because they are too expensive, I would like to know where these parts are located and how to clean the EGR sensor and

spark plug wire. The first thing you need to do is find out what diagnostic trouble code is in the computer and to save money autozone will scan it for free. Send me a message and tell me what came up