This pertained to my Audi, but the technology and solution should be universal.
I had a very common problem, a CEL for "incorrect purge flow" which generally means a clogged purge valve. The purge valve routes fuel vapors to a storage canister until the motor is running then allows engine vacuum to purge the canister. Simple. Until it breaks.
I took mine off, blew both ways through it and put it back. Was good for a few days, came back.
Then i got more serious. I took off the valve and carefully looked it over. One end has a brass fine mesh filter on it, so black with carbon or dirt that it is invisible inside the black plastic. I too it off and cleaned it with gummout. Next i cleaned the valve with gummout, and blew through it (both directions, just to be sure).
Finally, i put preventative care in place. I got a clear plastic fuel filter from a lawnmower. I got a length of the tubing used for the purge flow, and spliced this cheap-O filter in series with the purge valve. 3+ weeks later, problem appears to be gone, and if and when it re-occurs, its a $2.00 part.
Maybe this will help you.
Grant
Grant
gee-lenahan-at-gee-mail-dot-com