I’ve tried to import my cars from 4.1 to 4.2 and every time I get a Lua error and my cars are missing their engine.
This is the error for one of the cars:
https://pastebin.com/FBsXumwU
Troubling LUA error, i hope devs will solve that in adequate manner.
As for your engine “problem”:
That works as intended. You are going to remake the engine and rechoose everything after the engine.
There were many under the hood changes in engine calculations, so it doesnt seemed feasible to try to hook up some kind of advanced converter for purpose of reimporting car as it was
And lot of stuff afterwards has received updates, too