2000 Toyota Celica code P0505

My 2000 Celica's engine light keeps coming on/off. The code is P0505. I have read a lot on it. I have changed the air filter, cleaned the Mass Air Flow chamber and element, cleaned all connectors w/electrical cleaner, cleaned the throttle body without taking it off with cleaner and soft toothbrush. Light keeps coming back on. Would it do any good to take the IAC valve off of the throttle body and clean it or would I be better off buying a new one? It would seem the only place to buy the gasket for it is the Toyota dealership.
Also, could it be a vaccuum leak? If so, how do I know where they are?
What about the PCV valve? Could that cause it? Thks, Ken

Did you open the throttle plate when you cleaned it? If it is good and clean then the IAC is probably bad. Cleaning them usually does no good.

First of all, thank you so much for what you guys do to help us out!
Yes, I did open the throttle door and cleaned it as best I could. Upon restarting, it seemed the rpm's were a tad higher but the next day the light came back on with the same reading. I called the dealership and ordered the gasket (o-ring). It will be in Wednesday. They said they usually try to clean the IAC first. What is the best way to clean them? I saw where one person used pipe cleaners, another went to Sears and bought some cleaning accessories for $10.00.You stated it us usually bad and needs replacing anyway...does cleaning them ever do the trick? Also, I saw one link where you could buy the IAC motor for the valve for $40.00, is that an option? What is it that actually goes wrong with those things? Thanks. Ken

sometimes the electrical part goes bad and sometimes they just get carboned up. We dont clean because we have to warranty repairs and if cleaning only temp. fixes we have problems But you can try to clean it out and see, all it can do is not work.