Jack,

A couple of things you should check,

Hot water temp.

The water temperature in the tub on the first fill, should be a minimum of 120 dgrs.

Water level.

The water level in the tub(after the initial fill and 2 to 3 minutes of wash time, should be as high as the bottom of the heater element.

Water hardnesss.

The harder the water hardness the more detergent you need to use.
(if you're on city water, the supplier should be able to give you an approximate range or you can pickup a hardness kit at the local hardware store).

Since you can't control a prepackaged detergent or combination detergent,
I've(along with most most of the people in the field) always reccomended a plain powderred detergent, and a rinse aid additive, if needed for spots or desired by the consumer.

There's quite a bit of difference between a newer dishwasher(5-10 years)and an older (10 -15 years)due to new energy requirements and designs.

I think you'll be a lot happier with the unit operation,once you've done these checks and changes.

Drop us a line, if you need more assistance, or let us know how things are in a few weeks.

Good Luck,
:) :) :)