Idles rough

It can be failing and not throw a code. That is one of the things that is frustrating about electrical diagnosis. Parts fail slowly or intermitantly and until the senor fails or goes out of its' specified range, (performance can still be affected when part is within specified range), it is hard to track down the failing part.
The mileage you have is not really where I would ussually see one fail, usually closer to 100,000, but it all depends on the wear and tear and maintenance on vehicle. Of course. Things just happen as well.
I think the next step would be to either run some high quality fuel system cleaner, such as SEA FOAM or BG44K, and see what that does. Run a can or 2, which you might have to go to a service station to get, and be prepared to change the oil afterwards as they are so good at removing deposits it tends to dirty the oil up when used.
The other things I have in mind. If I have not mentioned already, are fuel pressure and possibly a failing fuel injector. You might check the fuel pressure manually witha gauge at a test port which should be on the fuel rail.
Try that and the fuel system cleaner first. If that does not work, it is getting near time where the O2 sensor should be replaced, by the way if you have seen a change in MPG that is a indication that it is going bad, as it is nearing the mileage I would suggest it be replaced. It never hurts eithr as MPG will be optimized as well as air/fuel ratio.
See what that does then get back to us.

You have a lean fuel condition can be caused by:

* Low fuel pressure due to a weak pump or leaky fuel pressure regulator. (Use a fuel pressure gauge to check fuel pressure at idle)

* Dirty fuel injectors. (Try cleaning the injectors)

* Vacuum leaks at the intake manifold, vacuum hose connections or throttle body. (Use a vacuum gauge to check for low intake vacuum)

* Leaky EGR valve. (Check operation of EGR valve)

* Leaky PCV Valve or hose. (Check valve and hose connections)

* Dirty or defective Mass Airflow Sensor (MAF). (Try cleaning the MAF sensor wires or filament with aerosol electronics cleaner. Do NOT use anything else to clean the sensor, and do not touch the sensor wires)

P0300 Random Misfire normally points to vacuum leak and bad fuel

Failing O2 sensors will as a rule sent the ECU into a rich mode, this will often account for poor economy and may also be the cause of the stumble, with that said, have you done a fuel rail pressure test as this can indicate a leaking injector that will also give the same problem as well, wort considering doing the test.

As far a fuel system cleaners go, you would not believe the difference in SEA FOAM and especially BG44K. BG can go for $20+ a can, but nothing else comes close to working like it does.
You will need to get some WD40 or PB Blaster to saok the sensor to ease its removal. You can find it in the exhaust path after the manifold but before the catalytic converter.
You will also need a special sovet to remove it if you connot get to it or have room to turn a wrench on it. It will have an electrical connector on it that you will have to trace up to the connector which will probalbly be as far in as the engine compartment.
I would really give the BG or SEA FOAM a chance, but plan on changing the O2 sensor anyway. Other Items that may be dirty and affect performance are the Idle Air Control Valve, which handles changes in engine load, and the Fast Idle Thermo Valve, which acts like a choke. You can try 2 cans of Bg which works so well at removing deposits, you will need to change the engine oil after using it from all the gunk it removes.
You may have to remove the throttle body and clean it and the aforementioned parts as well.
Having the lift kit will drastically change MPG, so don't consider that.
Let me know if you need anything else.

I have been researching your problem and found the following things;

There is a coolant sensor called a CHT, acronym. Don't know what it stands for, that can fail and cause idle problems.

The Ranger does not have a seperate FIT. It is part of the TPS and IACV working with the CHT.

Your truck has a reputation for motor mounts that get loose and cause a rough and/or shaky idle.

Since your truck is dropping in idle after warm, the."FIT Circuit" or choke circuit is working. That also means that the temp sensor is probably fine.

Since you reaplaced IACV, I found that a lot of Ranger owners helped idle issues by cleaning intake by either spraying cleaner down the TB when running, which I do not reccomend, or using Sea Foam or taking the TB and Intake apart and cleaning it.
How dirty were the small ports, or any ports that looked like they would connect with intake tract, as far as deposits?

From what I found you might check your motor mount with the standard, "Give it some gas with the hood open and the parking brake on", to see if motor moves more than it should.

That and the cleaning thing are the best options you have as the next moves to make. I don't think there is really anything, "wrong", other than possibly the motor mounts, with the motor or its idle unless its something we covered.
Those are all things you can take your time with. However, I would check into the motor mounts as that could cause you some problems.
If you find they are bad, check into Energy Suspension or other Ploy Eurethane motor mount inserts. They go into the motor mount and fill the gaps around the rubber to stiffent the mount. Some people say it is good enough to even repair a motor mount.

By the way, do you have the V-6 or the 4 cyclinder? Of course the V-6 is a little more prone to quicker mount failure but the mounts still fail on the 4 cylinder as rubber just does not hold up well with time and constant load shifting.

I hope the information helps. Definatly let me know if the mounts are bad as I always like to know if certain vehicles have issues with certain parts. The Poly inserts are not so hard that they will hurt anythng or feel rough, so don't worry about that. You can get shifter and suspension bushing replacements, practically all bushings, which I have done on my car and it does not make anything harsh or vibrate or add too much load transfer as they still give under load. I think sticking with just the mount inserts is fine but I heard a lot of the four wheel guys like them for the decrease in body roll. Especially if you have anti-roll bars and get the bushings for those.
Let me know how things pan out. I would not mess with the O2 sensor as of yet. But maybe plan on replacing it at 100,000+.
The mounts and cleaning intake really seem to be the most likely leads givent what I found and all that you have told me.

As far as the Sea Foam, it makes the oil dirty. I did not mean to add the Sea Foam to the oil. It is just that all that the removed deposits will end up collecting in the oil and it a good idea to change it after using it in the fuel system.

There are 2 ways to use Sea Foam. The first is to add it to your gas. The second way works better, but creates a lot of exhaust smoke for several minutes. To use Sea Foam directly into the intake is better as it is more concentrated as you pour it into the vacuum hose that goes to the brake booster.
First, disconnect the hose from the brake booster. The brake booster is the large circular thing that the brake master cylinder mounts to, which is mounted to the firewall on the drivers' side.
If you can get a funnel that will fit into the hose. Once you have the hose off, put the funnel in the end of the hose. Again, you will be disconnecting the hose at the brake booster and pouring it into the intake through the hose. Sometimes it might make it nearly stall at first. If you can get the help, have someone open the throttlr body by hand. Only open it enough to keep it running. DO NOT REV THE ENGINE HIGH WHEN USING THE SEA FOAM DIRECT POUR METHOD. ONLY HOLD THE THROTTLE OPEN ENOUGH TO KEEP IT RUNNING IF IT WANTS TO STALL. It usually does not. You will start to see tons and tons of smoke coming out of the exhasut. This will continue for several minutes, so don't worry. As soon as you finich pouring the Sea Foam in the intake, re-attach the hose to the brake booster. Let the truck idle until the smoke stop coming out of the exhaust and then a minute or two more. Let it sit for a couple minutes and take it for a ride and you may experience some more smoke and rough performance for a few miles. Eventually this will clear up and your really cleaning the intake tract as best you can without taking the intake apart.
You will definately get the oil dirty doing it this way.

To recap the direct intake method;

1. Disconnect hose at brake booster
2. Put funnel onto hose end
3. Pour Sea Foam into the funnel so it will go into intake manifold
4. Keep the engine running by hand if necassary, DO NOT REV ENGINE MORE THAN NECASSARY TO KEEP IT RUNNING. DO NOT REV THE ENGINE HIGH DURING CLEANING PROCEDURE
5. Allow smoke from exhaust to dissipate for two minutes after it stops smoking
6. Let it sit with engine off for a minute
7. Drive it normally until it clears out the rest of deposits
8. Check and/or change the engine oil as it will get dirty from removed deposits settling down or running down into the engine oil

This will really make a difference. You might experience some strange performance from the motor for the first 10 miles or so after using it as other deposits are removed when you rev the motor and drive it more.
Let me know how it turns out.

Change the oil when it looks dirty. It all depends on how dirty your engine is.
If it does not smoke much don't worry. It is getting sucked up by emissions stuff. Every motor is different, I just did not want you to freak out if it happened.

Did you get a chance to check the motor mounts? I found a lot of stuff about not only the motor just being a rough idler, but the motor mounts are notorious for wearing out fast.

I think it really works best when the motor is unning to disperse it. Then let it sit and soak. Meaning. Don't just pour it in without motor unning and let it sit. Do it with motor running, then stop motor a few minutes and start back up. Another can in the tank cannot hurt either.
I think to get any better results, you would have to take the intake apart and clean it.
I think that with everything said and done, I would leave it be unless the rough idle really bothers you. Eventually you will have to take it aprt and clean it. But not now.

Just a thought that when you do the timing belt, which is suggested by Ford to be replaced at 120,000 miles. Alot for a belt, you could do the intake then since you will be in it for a day or so. I read the instructions for timing belt replacement on the 2001 4 cylinder 2.2L and it seems pretty simple to replace the belt. None of the intake or any thing besides the A/C and some tensioners come off.
I think between the code running and your friend and us your truck has been well looked over and it just is not a Mercedes when it comes to the idle. No big deal, but it was smart to make sure that it was not something that was a big deal. Spend $100 in maintenance and save $1000 in repair is a true statement that I hold to.
Keep up the maintenance and your going to get another 100,000 miles out of it.

Dr. C

You can jack the truck up and put a jack stand unser it for safety.
Then grab the tire and pull and push on the bottom and you will fwwl if it has play or not.
Almost any truck with 60,000 miles or more on it needs lower ball joints. Four wheel drive trucks are especially tough on them.
Make sure to get some good ones that have a grease fitting. MOOG is probably the best brand for replacement suspension stuff.
The best on line parts stores are US Auto Parts and RockAuto. Com. Rock Auto has closeouts where the warrantee is forgone but the part will be %50-%70 cheaper.
Lower ball joints just see a ton of stress from big tires. They will come apart too, so don't worry about sympatamativ behaviour. Just replace them every 70, ooo miles. You can just thread the castle nut on a few turns and beat the old joint out. Go to an advance auto and borrow an install kit or use same size socket to beat the new one in. Its not too hard a job.

No, they come with grease fittings. Just wanted to make sure you did not get Chinese ones without them. Most imports do not have fittings and are not serviceable. Is that ridiculous or what?

I am not too familair with lifts. But the angles that the components will see are greater and therefore harder on components. I am sure if you look around you can find upgrades. SummitRacing. Com is a good place to check with good prices.
The best place would be to join a Ford Ranger enthusiast forum. They are all over the web and are full of aftermarket links, reviews and usually a market place for new and used parts that are hard to find.