Don't know how it could make the engine rev like it was in neutral but I had and old POS 66 Buick when I was 17 that had mechanical throttle linkage and a motor mount broke letting the engine raise up and pull the carb wide open. Good thing I wasn't behind someone when I first happened. Took me a little bit to figure it out cause when I'd shut the key off the engine would drop back down and let the throttle up.