High idle and poor mpg
My car randomly idles pretty high (around 2000 rpm) and I've noticed my mpg has suffered. I only got about 250 miles out of a tank of fuel. I like to think I drive pretty sensibly. I had the check engine light scanned and it came back with evap system small leak p0442 and catalyst system low efficiency bank 1 p0420. At the top of the printout for the engine light it says "ASE certified mechanics have seen this issue on your type of vehicle and the most likely solution is replace fuel tank pressure sensor.
I was ready to do this but I was told that the fuel tank pressure sensor doesn't affect how the engine is running.
Could the idle and poor mpg be the sensor? A vacuum leak? Something else? The car otherwise is strong and has no knocks ticks or other issues shy of a broken exhaust hanger.