2007 FXT Limited 5 Speed Manual
Hmmm...multiple applications of cleaner to the tank and it prolonged it each time... Mine spit out the P4220 small leak code and I already had a brand new Subaru Cap, so I cleaned the mating surface and gasket of the cap. Then added some Marvel Mystery Oil to the tank and had a small trip out of town, but the CEL flashed again when I was almost home, but this time the code was the P0456 very small leak. Each time my CEL triggers it is when I am driving on the open road. I can drive in town and it will never come on, but a few hours of highway driving and it triggers. I need to dig around like @Ski-Free is doing just to verify the status of things, but I am wondering if mine just needs some more cleaner ran through it like you did.yes, you should be able to blow air thru when open, no air when closed. The problem with the old valves is that "gunk" can get inside and coat the inside of the valve and it won't "fully" close. So after I changed my valve, I had a smaller leak from the other old valves in the emission system. I could tell it was getting better because the time between CEL was longer. So I tried cleaning my emission lines with Berryman B-12 (no difference) and then SEAFOAM. After the first bottle of SEAFOAM in the gas tank, the CEL didn't come back for 200 miles. When it came back, another bottle stretched the CEL to 600 miles. Third bottle and I am up to 1000+ miles. So far the SEAFOAM is working for me.
I have heard from Jackie that 2007's, and I am guessing it might include '06 thru '08, that the canister is an issue with these models. The vent valve is part of the canister too. I don't know it is just XT models or if it across the board. I didn't ask her that because mine is the on the problem-child-list when it comes to canisters.
Once in a while I can smell gas fumes, and other times I cannot. Like earlier this week, gas vapors were present when I was downwind of the car, now they're not. When I could smell them the tank was near 1/4, now it is full. I want to drive it on the open road to see if the CEL will come back but right now it is parked for the upcoming timing belt replacement. While it's down I need to also inspect the filler neck and canister area.
I will be following this thread to chime in on what I find and to see if you were able to fix yours. I have emissions testing in June 2019 and I need to make sure this issue is fixed for good.