Any ideas what could be the cause of inaccurate and uneven heating with a Whirlpool electrice accubake oven? The stove elements heat up fine and the oven works but not properly.

There is a splice in the 220 line to the range. Is it possible this is causing the problems. If so how do I test?

A properly done splice will not create a problem. It sounds like your thermostat or the thermostat sensor has gone out of range. Some are adjustable with the proper tools and a high temperature heat meter others will need to be replaced.