1999 Toyota 4Runner Check engine light goes off and on

The check engine light has been going off and on for weeks now. I took it to a neigborhood mechanic who cleaned the cylinders and told me it would be alright. Then the light came back on and off again. I took it back to same mechanic and was told it was a bad wire, which he replaced for forty dollars. He told me it was alright. Then the light started coming on again, off and on. I took it back to him a third time and he told me it was a bad coil and it would cost over 300 dollars to repair.

Then I took it to the place where I get my tires rotated and they told me the light was on. I said I know and they asked what was wrong. I told them about the bad coil and they said that the 4 runner doesn't have coils.

Then I called the dealership and they told me unless I took it someone who has a Toyota computer, they were shooting in the dark. They said the 4 runner does have coils and it would cost around 200 to diagnose and repair. They also said I probably wasted my money on the wire replacement because it would have to have been misfiring to need a new wire and it wasn't misfiring. It's just running rough. So I guess I need to take it to the dealership to find out what's really wrong with it and get it repaired there.

Do you have any insight you can share with me on what's really wrong with it and how much it will take to repair it?

Thank you