94 SL Engine Light Question

I have a 1994 SL with 95,000 miles. My engine light has been coming on fairly regularly over the last several months. It occurs usually after 20 minutes or so of start and stop driving, or when the weather is very warm. When the light comes on, my engine immediately surges RPMs and then it will begine to pulse up and down when idling. This pulsing gets so severe that it fells like the car will die at the intersection. Once I apply the gas, though, the car seems to run properly. I have not had any work other than oil changes done in the past 10,000 miles or so, and am not losing any fluids. Can anyone recommend what I might be able to do to fix this problem myself?

start by pulling the code - http://www.differentracing.com/tech_articles/diag_info.html