1986 Ford Bronco

I have a 86 bronco 2 with a 2.9 and a 5 speed. I was driving on a dirt road and my rpms dropped from about 2000 to almost stalling and instantly went back to 2000. This happened once and as I kept driving accured more often. Then it would die and I would have to turn the key to start it back up while still moving. This happened more and more until it wouldnt stay running at all and wouldnt start at all. It will turn over like normal but just wont fire. I am getting spark and fuel. I have done everything I know to do to get it running and I have came to a stuck place.