Whats wrong with my 95 chevy astro van idleing real rough, it sounds like it wants to cut off but it doesnt?

well it was sitting on a hill for a couple months without being started. It hardly had any gas, it wouldnt turn over the other day when we tried to get it to a few times but nothing, then we but some gas in it from our house and got it to the nearest gas station 5 minutes away, im thinking trash got up in the line because it was taking what was left in the bottom of the tank when we tried to turn it over, it never did this the last time we drove it . the service engine soon light comes on every once and a while. driving and giving it gas it sounds fine, but the idle is real rough, what could be my problem