Problem Question

I own a 1990 240sx and im having a few problems.

I have the original KA24E and whenever i start it, it wants to die. So far, i have not been able to find the problem. at first i thought i was getting no spark. i checked the cap and rotar and all seems to be working fine. however, when i checked the spark plugs, i found oil and what i think is carbon build up. From this, i guess im running rich (im a newbie) any suggestions on the problem?

thanks.