Ok I keep getting a large evap leak DTC. P0455. I can clear it and it will stay away for about a week. Usually it kicks on when the car is first started and then will remain on...sometimes if I don't clear it, it will go away on its own after a day or two...but it will return. I have changed the fuel cap with an OEM one as the one on the car was an aftermarket one.

Short of spending $80 for someone with a smoke machine to diagnose this thing, any ideas? I hate to throw parts at it but a couple quick things may be worth it.

The car runs perfect with the exception of a transmission issue that I need to address soon.

 

You may want to check this link possible solutions. I noticed you already replaced the gas cap but did you check to make sure the cap has a seal present? If the cap is OK then a vac leak may be the culprit. Check all the vacuum hoses, specially the ones going to the evap canister, for leaks. Good luck!
http://www.obd-codes.com/p0455

 

I am having the same problem. My mechanic doesn't have a smoke machine (small mom and pop shop) but he checked the entire system looking for bad hoses/leaks/etc and never found anything. He did replace the gas cap but we're waiting on a new OEM fuel line to be shipped in (unrelated issue) so don't know if the cap has solved the problem yet. Thankfully since he doesn't feel he fixed it he's not charging me for all the time spent looking through the system.

I think I'm going to have to go to a shop that has a smoke machine.

If you find out what the problem is please post

 

this could be the sensor in the fuel tank attached to the fuel pump. even if you had a leak in you evaporator. i wouldnt care about it. if you want it fixed your probably going to be replacing the pump. so if i was you, i wouldnt care about it.