Hello, I recently got a 1999 3.0 flex fuel automatic ranger with about 140,000 miles from a goverment auction. The check engine light is on and is says misfire cylinder 5. I replaced the plugs and the coils and with each repare it got a little better each time. It has a bit of a rough idle, not a lot of power, and when going 50-60mph at low rpm’s the engine bucks/shakes.

Any help anyone has would be greatly appreciated.

 

I'd suggest doing a compression test of all cylinders. I had a 2007 Ranger with the 3.0 engine that had almost the same issue. Rough idle, and misfire codes. I also replaced everything I could think of to eliminate the problem. Nothing help. So I put it in the Ford garage and they determined that I had receding valve seats. They said that the fix would be to pull the heads and do a complete valve job including installing new seats. The truck was scheduled to go into the shop on a Monday to have the work done. But on Saturday, my truck was stolen and totaled in a wreck. I now drive a 2010 Ranger 4X4 with the 4.0 engine. A compression test might give you an answer.