I have a 1990 Geo Tracker that also was doing the s/a thing. After changing
fuel filter, new plugs, etc. etc. it still did not fix the problem. I
noticed that when I would put my hand to the exhaust, I felt nothing
coming out which indicated a plug in the exhaust system. It turned out to
be the catalitic converter was plugged. Once the converter was unplugged,
the car runs great now.