Had CEL for emission system, computer says small vapor leak, cleared and assumed I didn't tighten gas cap, cel light reappeared in two days; smoked the car, no leak detectable. Filler cap valve replaced in 08 when service bulletin issued. Anyone experience this issue and/or have a resolution? I am replacing filler cap valve to start. Any help would be greatly appreciated

 

I would start with that too, but in most cases a gross evap leap is caused by a loose gas cap.

 

U smoke tested it, how did u deal with the DMTL valve? Did u block the port or electrically cycle the valve closed...other wise u would of had smoke pouring out