Engine 4 issues
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This sounds like there may be some sort of control assignment conflict causing the engine to stay at 100%.
The easiest way to test if this is the case is to unplug any external hardware you have (joysticks, throttle quadrants, etc) and then load a into the Vulcan on the runway. Then use the F1-F4 function keys on your keyboard (or your mouse) to vary the throttle positions. If the throttles are working correctly, then that suggests there is a control assignment conflict related to your external hardware.
If you then plug your external hardware back in, then go to MSFS Options > Controls Options, click on one piece of your external hardware at the tabs along the top of the screen and then search for any "ENGINE", "FUEL" or "THROTTLE" control assignments. As you're only having issues with engine 4, the conflict may only occur on a control assignment that is linked to the number 4 engine (for instance, SET ENGINE 4 FUEL VALVE).
Hope that helps.
Mark - Just Flight
