1992 Toyota Corolla DLX wagon misfiring and jerking

What is your question?

After driving a few miles, check engine light will flicker rapidly and car will start to jerk and misfire. After about a mile or so, the car will drive okay, but check engine light stays on. When you turn car off and on again, there is no check engine light. I changed oil within the past two months, and it is now black, not golden colored. Spark plugs were changed earlier this year, and there is soot on them. Any idea of what is going on with the car? Very frustrating.

What makes this problem better or worse?

When engine is warming up while driving

How long has your 1992 Toyota Corolla had this problem?

For many months. I had to let car sit awhile. Did not have time to keep working on it.