I could be wrong here but most late 90's cars do exhibit noticeable vibration on the body while the car idles are low rpm and it's fairly noticeably as well and heard. Its quite cool two and shows the engine is quite strong and healthy. Most cars in beamng should feature this except the ETK K series
Actually, most cars do not exhibit this behavior from that time period. The only cars that may do this would be something with an American V8 in it, but even most of those were fairly smooth even by early 90's standards. This is more of a 60's till 80's thing where the huge American V8's were carbureted or just getting to grips with fuel injection. My 81 K10 truck for instance pretty much never idles smoothly (but it's also got a ton of modifications to the engine so who knows what all is going on in there) as it is carbureted with a manual choke while my 84 Corvette will idle fairly rough when cold, but smooths out to a nice, calm, almost placid idle when warmed up thanks to it's (even if early) fuel injection. By the time the 90's hit, just about everything was using fuel injection and ran very smoothly. Over the years they can get gummed up and start to run rough, but that is hardly the definition of a healthy engine like you mention. Of course, if the engine is modified, with say a much larger cam with a lot of overlap, then all bets are off... anything can have that big, meaty, choppy idle at that point... which we kind of can do in game, so then this would be a nice thing to have... but essentially the only thing that would be needed would be something like idle stability (seeing as engines already can apply torque to the cars from changing revs), or how smooth the idle is. This could also be affected by the temperature of the engine as well with it running rough when cold, but once it warms up, smoothing out to a nice calm idle.
