Okay, let's try it a different way.

In you original post you were thinking that deposits (presumably glowing) were the problem. In order for them to be a contributor to run on they would need fuel to ignite. In order for fuel to get from the carb bowl to the combustion chamber you need air flow. If the throttle plates are completely closed there won't be air flow to siphon fuel from the carb bowl and through the rest of the intake system to the combustion chamber. There are the tools, you need to do the diagnosis.