It will be closed all the time without the engine running. The spring heats up and lessens the tension when running. Either the stop is missing or it is assembled incorrect.
After looking at it further, I think you are correct in that the stop is missing. The stop should hold the plate in the closed position when cold, and the spring when heated, will open the plate 90 degrees. What is happening now is that the spring allows the plate to move 180 degrees, back to the open position.
Thanks for your input. Now I just have to figure out what it is that should be stopping it in the closed position.