Check engine light is on.

I have a 1996 Honda Accord. Two years in a row, the "check engine" light has come on. When I took it to a mechanic, both times I was told that it was an emissions problem.

The same light came on again last week. The car is driving very poorly. It starts okay but then has a hard time driving. It moves slowly, no more than 30mph. After about half a block, it just stops. It doesn't stall, it simply stops moving. Then, after 10 seconds, it'll start driving again. A few seconds later, it stops again. It's like it's having a fuel pump problem or something. According to the manual, though, it's an emissions problem.

Any clue what it could be? I don't want to take this old car to a mechanic and pay big bucks to fix it. I'd pay a smaller amount, though.