The Service Engine Soon light comes on in my 1993 Chevy Lumina. I just recently started having this problem. When it first started, it wouldn't come on in the morning driving to work but on the way home from work, it would come on about 5 to 10 minutes of driving then it would go off about 3 minutes after. This was about 2 weeks ago. Now when it comes on, when I slow down or come to a complete stop and then accelerate, it feels like its having troubles/ being slow at accelerating. But once I get up to speed, it stops and the light stays on for a while. I've checked oil, tranny, and coolant levels. All are at the proper levels. Oil is changed at 3,000 miles. Mileage is currently at 129,000. I've been told that it could be the O2 sensor but they weren't really sure. Any ideas on what it could be?