[thephantom1492]

P0440 is a Evaporative Emission Control System Malfunction code.
What it basically mean is that you have an air leak in the fuel tank, or a faulty solenoid. Basically, the venting of the fuel tank go to a canister that absorb the vapour. From time to time the ECU trigger a solenoid that suck the fumes out of the fuel tank, causing the trapped vapours to go back in the fuel tank, and back in the engine. To test for leak, a solenoid block the vent. A partial vaccum should appear in the tank. If you get a P0440 it mean that when it does block the vent then the vaccum do not reach the set point. This can be caused by a faulty solenoid, fuel cap that you don't tighten enought when you fill up, defective cap, air leak, or faulty vaccum line and other stuff.

It is possible that you have a vaccum leak (hence the P0440), or fuel pressure regulator that is failed. Also, the IAC could have issues. If you do not have misfire code, I'ld be tempted to say that you have too much fuel, so would investigate the pressure regulator first I'ld also check the IAC. Somewhere I'ld also check the wiring and spark plugs. While checking the spark plugs, it is a good idea to compare each other. If one look different than the others then I'ld investigate on why. It might be nothing, it might indicate a problem there. Ex: if one plug is wet, but the others are fine, then you probably have a problem there: you have unburned fuel (or oil, hopefully fuel) on the spark, could indicate a stuck injector or a no spark. Both could make gas smell on the tailpipe.