I recently bought a 05 ranger FX4 4.0 non running after sitting for 2.5 years. I replaced the computer, and fuel pump and it started right up. Drove it about two weeks and it developed a misfire on 1-2and 3. So I replaced plugs,plug wires and coil pack. The original owner told me he replace the injectors before he parked it. Now the engine light comes on and when it drops below 1200 rpm it begins to flash and looses power. If I idle it above 1500rpm the misfire will go away the flashing engine light goes off and it smooths out. I don’t know what else to check. Thanks for any help you can send my way.

 

I'd try a fuel system cleaner like Techron and check the delta exhaust pressure reader gizmo because I hear they go bad with disuse.