Take him to neutral territory eg a pub and tell him this incident has been bothering you so much you could not let it slide.
The conversation then becomes about letting the incident slide rather than him trying to kill you which will be obviously easier to handle. You can then always get round to the ‘are you trying to kill me’ question which never comes out quite right
Alternatively, chuck a couple of kippers in his engine bay (try and wire them onto the exhaust manifold), the stink will NEVER go away and he’ll NEVER be able to sell the car when the smell permeates his clothes / home / workspace.
(Completely true and a very nasty thing to do which I’d never condone)
Tortoise p*ss is a very good alternative but hard to get hold of. (The tortoise tends to fall through the gaps in the engine bay anyway)