I have a 2004 Ford Ranger 2.3L 5 speed with 135,000 miles that is having the surging problem. It does it worst around 2000 RPM's, but does do it across the entire power band. I have replaced plugs, Wires and cleaned the MAF. At this time it is not throwing any codes.

Any help would be greatly appreciated. Thanks

 

-try and catch a pending code

-change fuel filter/fuel pressure

-vacuum leaks

-check/change air filter and intake

 

The IAC is responsible for engine idle speed, so maybe consider removing & cleaning it with a plastic safe spray & see how it goes.
Cleaning may not last, it didn't for me, but was a good trouble shooting step. It can act out & not set any trouble codes.

Put the PCV valve & it's plumbing on your suspect list too, as it's time for replacement & I believe Ford does it for free on your engine. Maybe the vapor recovery system also if you don't have joy cleaning the IAC.

More thoughts for consideration. Let us know how it goes.