I'm having the exact below issue (seen on the YT video); I replaced the IAC valve (Motorcraft) with no improvement; the TPS sensor has 50k miles on her; I checked the grounds, and they are clean; I checked and found no vacuum leaks; coil packs are clean (no corrosion around ignition wires where they seat into the coil pack); the fuel filter has 60k on it, and I use top tier gas. I am an amateur at best, so please keep that in mind when replying. 2001 2.5L, 5 speed, with 216k.

The guy in the below video replaced his ICM, and that may, or may not, have fixed the issue; from what I understand, the 2001 Ranger doesn't have an ICM.

I should add that the truck drives good, has plenty of power, and pull strong; the only issue is the idle issue.

My main concern: I take long rides with the truck in rural areas; will the below issue leave me stranded? Thanks.

 

Your 2.5l Lima engine can run fine on just 4 spark plugs, did so from 1974 thru 1988, just FYI

After engine is warmed up shut it off and open the hood

Unplug the 3 wire connector on either coil pack, move it far enough away so it can't ARC to coil pack
Start engine
See if there is a steady misfire, if so then one spark plug or wire on the working coil pack is bad
If it seems OK then go for a quick drive, it will have slightly less power but no other running issue

Then repeat but swap coil packs

This is to make sure all spark plugs are working like they should
Dual spark plugs were used to get more power from an engine, so both spark plugs fire at the same time or there would be NO POINT in having dual spark plugs
I often read about "alternating spark", beside being a dumb idea, lol, there would be no point of dual spark plugs, no benefit
But one of the draw backs is that you can't tell when just one spark plug is not working, lol

4 valves in one cylinder added even more power so was a better use of "head space" than dual spark plugs, so that's what is used now on most engines, although there are still dual spark plugs engines around


Also add a can of Seafoam or similar injector clean to the gas tank
Dirty injector tips can DRIP fuel instead of spraying it
With the lower air flow at idle this uneven air:fuel mix can cause misfires, and stumbling engine, which goes away at higher RPMs because of faster air flow and longer open times for injectors

Yes, 1994 and earlier Rangers, and other Ford models, used the older EEC-IV Computer(PCM) these were 60-wire and did not have an internal Spark Module(ICM), there there was a separate ICM(ignition control module) on the engine
In 1995 Rangers all got the new EEC-V computer, 104-wire, OBD2 that did have an internal ICM(spark module)

 

Thank you for your extremely helpful, informative, and easy to understand, reply.

I did run a bottle of Techtron through the system; the first time I had seafoamed the engine, I got a lot of white smoke coming out of the exhaust; subsequent times showed very little white smoke/carbon blow off.

I'll give what you suggested a try, thanks.

 

Okay...I only now saw your comment about swapping coil packs.

I idled the struck for 15-20 min; I observed that the very rough idle/almost stall, followed my an idle surge, is intermittent.

I then unplugged the front coil pack and let it idle for 10-15 min; the idle was very rough but consistent; no dips or surges. I let it idle for 15 min; no change.

I then unplugged the rear coil pack, and the idle was rough, but it stayed solidly at 950rpms. I also let it idle 10-15 min; no change.

FYI: I checked the plugs 25k ago, and there was virtually no wear; the wires have 75k on them.

 

Your suggestions were spot on Ron; thanks so much for your helpful diagnosis.