02 grand prix code 0440 gas mileage

[Boneyard]

I have a 02 GP 3.1L. it shot a code to me of p0440 and I checked it as evap. what are the common problems with this code. I've heard gas cap, but replaced it and it still comes on. Also, I checked my gas mileage and I was getting 29 and now it's dipped to 23. what could be the cause?? thanks for the help

[BNaylor]

When you replaced the gas cap did you clear the DTC and SES/CEL light with a scan tool or get enough drive cycles on it? Link below may be of some help on the large leak.

Click here

[Boneyard]

I cleared it with a scantool. the gas mileage is my biggest concern. should a leak in the evap kill your gas mileage? thanks

[tblake]

if the leak is large enough.... yes. especially during these hot summer days, a lot of gas can evaporate.

[BNaylor]

Evidently the leak is large enough otherwise it would just give off a small leak DTC. I would say if there is a vacuum leak a loss of gas mileage would result because the short and long term fuel trims get whacky. A vacuum leak causes a lean condition which means the fuel injection system goes richer to compensate.

I would start checking all the vacuum lines at the evaporative purge solenoid and back to the gas tank to include the charcoal cannister. Also, check the pressure sensor at the fuel pump assembly.