would lack of tune up on a van cause it to overheat or have idle problems?

Question

it is idled high even after idle sensor, thermostat, water pump, hoses, and trottle sensor has been replaced.

Answer 1

Not normally, but a vacuum leak will do all of the above.
while it is running try to listen for a whistling sound from the various small hoses. Check that one of the hoses hasn't fallen off its
connector.....

Too much air in the sytem will cause it to idle high, miss and overheat a bit.

Answer 2

You should have replaced the belt too.