Bad gas milage, random CEL and idle
 

Sorry, I used the searched and couldn’t find what I was looking for. So my check engine light turns on only after my car has ran and sat for awhile, I wake up at 8 go to work, drive home for lunch and back to work, then drive home shower and leave, light turns on then, but only for a short time, or it flashes on and off during acceleration, most of the time, and turns off not to be seen until the next day, also my car idle way low for the first time day after I drove some after work, stopped and started it, started fine just idled low then went back up to normal idle rpm, also I have super bad Fuel economy like 10mpg in the city is that good or bad, I just have an exhaust and a down pipe both 3", with a exhaust leak I believe, my car Backfired like a machine gun when I didn’t my car for like all day, anyway I would much appreciative if I could get some help on this stuff

i bet it's your thermosensor.

pull the codes and find out :)