Spark plugs

Chryslers come with Champion plugs with the Mopar name on them and they hold up well. I've heard of people having misfire problems with other brands of high quality plugs. The Champion number and specified gap is listed on the emissions sticker under the hood. Those numbers are half way down on the right side.

It'll be nice if we know the liter of the engine- 3-different engines involved

I've heard similar things about split-fire type plugs, but for my old stuff I'm always looking for the cheapest, ... Ahh, ... I mean "least expensive" way out. I just solved an intermittent running problem on my '88 Grand Caravan after 11 months, and against all the advice I could give someone else, I decided to replace my 12 year old spark plugs. No surprise, it didn't solve the running problem which, now repaired, still sort of defies logic, but my gas mileage went up a bunch. That was a case of penny-wise and dollar foolish.

I seem to recall that Autolite plugs don't perform well in Chrysler engines but that might pertain to older cars. I'm not sure what the advantage is to platinum plugs. If they last longer, that would be an advantage in engines where the plugs are hard to get to. If they create a hotter spark there might be fewer misfires, but if that hotter spark requires higher voltage to make that spark, it's possible the ignition coils can't develop that higher voltage. We could even get an engineer involved who would discuss the smaller electrode that might be partially shielded from the vaporized fuel. That could create a misfire in one engine but it would work perfectly fine in another brand of engine where it is angled differently.

I think I would first try a set of standard plugs that are called for on the sticker under the hood. If there is still a running problem, at least that will remove one variable from the list of possible causes.