pcv valve problems

Having a problem with the pcv valve. In short my SVX is idling rough and I thought I would start with the valve. Easier said than done. I located the valve, but can't get the thing loose. I am able to get my 19mm crow's foot on the thing, but it is frozen tight. I have tried liquid wrench to try to free up the threads, but as the pcv valve screws upward, I don't think any of the spray is actually reaching the needed threads. (By the way, I am turning the wrench the right way, which is opposite of normal because of the orientation of the valve) Any suggestions or tips would be appreciated. If worse comes to worse I guess I can take the valve I bought to an independent shop to have them install it, but I can't imagine they would have any better luck than I have, and I don't want to end up with a frozen valve with stripped threads.