Why does van quite running after 30 to 40 minutes?

What is your question?

computer diagnostics say it's the #1 plug--that along with wires and distributor coil have been replaced.Van starts and runs good when cold but after it shuts down it will not restart until the engine is completely cooled down.

What makes this problem better or worse?

it's worse after having driven it for a period of time, 30,40 minutes

How long has your 2004 Dodge Grand Caravan had this problem?

a few weeks