Take a lanc, start up all 4 engines.
Press Shift+1, e (turn engine 1 off)
Press Shift+4, e (turn engine 4 off)
let 1 & 4 spool down
Now - to control engines 2&3 at the same time - what do you do?
Press Shift+2+3? Nope - that only controls one of the engines
Press Shift+E? Nope - that selects all four engines and starts engine 4. NOT what you wanted. Press it again, it starts engine 1.
K