When you say poor starting, is that always? or only when the engine is cold? or only when the engine is hot?
When you say stalls occasionally, is that at idle? or when coming to a stop? Is the engine cold or hot or both?
The diagnostic connector is not OBD or OBDII. Look at this page to read the engine codes with a multimeter that has duty cycle:
Evaluating Electronic Engine Controls
or you can navigate to it yourself by selecting the D.I.Y. tab at the top of this page. If you don't have a multimeter that has duty cycle, Sears sells one for about $30. A search should come up with a model number.
When searching this forum, keep in mind that you have essentially the same engine as the 300E, 300CE, 300SE, and 300SEL from the mid '80s to the early '90s. Of those, the 300E is by far the most common. It's the M103 engine.