Volkswagen: engine run on after switch off- 1897 VW Golf MK11 1.8 auto., best guess, electrical system

Question
Hello, is there any cheap cure to this problem (cause carbon build up??) Often runs on and takes some effort to stop ignition. Never when cold. Temp. gauge usually on middle when up to temp. 130k miles. Thank you. Regards Paul.

Answer
I believe the ignition switch is bad, stuck/shorted to the ON position, because you need power to run all systems(injectors, timing, fuel pump, etc.)  Otherwise, there is another short in the electrical system which is supplying power to the ignition when it should not be there.  Sorry, I've never seen this problem in a modern fuel injected engine, so that's my best guess.