the other day when I was driving to work I pulled a SES lamp, a few days later I had it scanned, I came up with P0440, Evap system malfunction.

Also recently I have noticed the smell of gas near the rear of the car, now I just had my fuel tank out to change the fuel pump... about 1500 miles ago now, and the tank all around was good, with no serious rust on it. And another thing the best I have been able to get is about 21mpg doing mostly highway driving.

I did a search and came up with mixed results, I checked my gascap, and clicking it 3 times seemed to make the small go away, so that might have been part of the problem.

Also I pulled that solenoid off the charcoal canister and no carbon came out of it all around it seemed okay. It ohmed out to about 22.5.

Then I pulled the negative batt. terminal for about 10 minutes, when I reconnected it the SES lamp came back on immediately.

all the vacuum lines and hoses seem to be good, I'll check again when it is light out to be sure and I double checked my connections to the fuel pump and they all seemed to be nice and tight and there was no smell of gas in that area.

I had a chronic P0440/P0446 that bugged me for about a year or so. Check the tubing, to make sure they are not crushed. Start from the evap canister and it will lead over to the passenger side right along where the TAM (torque axis mount), pay special attention there. My EVAP tubing got crushed by the TAM when I replaced the serpentine belt, upon repairing that, the codes disappeared forever.

If all tubing looks ok, try replacing your gas cap, it'* cheap enough to test it out.

And for the gas mileage, it'* cold outside, is it not? winter gas will play hell on your mpgs, don't fret.

Update on the situation, I went by the dealer and got a new gas cap, first and foremost. I figured, why not since it is the easiest thing. No deice.

Then the other day I filled the tank all the way up, and a very strong smell of gas came from the back of the car, and all the fuel pump connections are good and tight as well as the filler and vent tubes. however I did just put a new fuel pump and sender in the car, and the crappy O ring that they gave me must be causing this, so another dealer stop and $8 later I have a good GM O ring that looks much better then the crappy one i got with the new sender. now come next weekend I will find out for sure!

hopefully the final update on this, I dropped the tank again, replaced the ring with the correct GM one, and put it all back together, and within about 10 minutes of idling the SES lamp turned itself off, I've put about 100 miles on the car since then and the fuel smell is gone, so all seems to be well!