When idling there is a loud hum until you engage throttle it fuel injector?

There are a few possible causes for a loud humming noise when idling that goes away when you engage the throttle. One possibility is that the fuel injector is dirty or clogged. This can cause the fuel to spray unevenly, which can create a humming noise. Another possibility is that the fuel pressure regulator is faulty, which can also cause the fuel to spray unevenly. Finally, it is also possible that the fuel pump is faulty, which can cause a humming noise.

To determine the cause of the noise, you will need to inspect the fuel injector, fuel pressure regulator, and fuel pump. If the fuel injector is dirty or clogged, you can clean it with a fuel injector cleaner. If the fuel pressure regulator is faulty, you will need to replace it. If the fuel pump is faulty, you will need to replace it.