Why is my 1990 jeep wrangler yj is running hot

My 1990 jeep wrangler yj 2.5l 4cyl is running at 210 to 230 in sometimes close
to 250 . when its idealing its normally stays at 210 but sometimes jumps to
230. On the roads it normally at 230 but jumps up to 250 sometimes. I replaced
the tstat,temp sensor, radiator, waterpump,fan, all the coolant hose's and I
flushed out engine block .I used 5050 coolant  and after all that I still have the
same problem. Oh and i checked if there was exhaust fumes going in coolant in
that was good . so does anybody have any ideas what could be wrong.