What is code #26 QDM Fault on 1992 Saturn SL2

The car overheats and has the smell of a strong odor,Gas fume type.
The service engine light comes on frequently and thens goes off. When the car is started in the morning it runs rough and stumples during warm up.When the A/C is on the problem is the worst with lack of power, overheating and foul smell.

Asked by for the 1992 Saturn SL2