Rough idle

My 98 Explorer 5.0 is running rough. It idles at around 1000rpms witch isn't bad but the engine shakes until you increase the rpms and it smooth's out. I cant figure it out. My idle control valve was bad so I replaced it and it helped with the idle. Another thing is when I put it in gear it drops below 500rpms and wants to die, and when its in gear it wont go past 2000rpms and that's with the pedal to the floor. If some knows what im missing please let me know. Im all ears on this one.

Does your Check engine light(CEL) work?

Is it on.

Cold engine should idle at 1,100rpms
750rpms after warmed up, 5 to 8 minutes

It reads like a vacuum leak, can you let engine idle until engine is warmed up, then unplug the IAC(idle air control) Valve, this will cause it to close.
Idle should drop down to 500 or engine may even stall, either is good it means no vacuum leak.
If idle stays high then you have a vacuum leak.
If you have tried to adjust what "looks like" an idle screw on the throttle linkage, then you will have to reset it because it is NOT and idle screw, leave IAC valve unplugged and adjust screw so idle is at 500.
This screw is an anti-diesel setting but can be used to fine tune TPS's(throttle position sensor) lower voltage, which should be .6-.9volts

Vacuum leak means lean air/fuel mix which has no "power" so shifting into gear and adding a Load to the engine can cause it to stall.

5.0l did have issues with intake manifold o-rings leaking
PCV Valve hose, and other hoses, unplug the hoses, one at a time, and plug intake port with your finger, when Idle drops you found the leak.

OK I'll give that a try. I tried the carb cleaner trick but couldn't hear any difference. I tried two different scanners and no codes.

How did you know the IAC Valve was bad?

Ok their were no codes after I replaced the IAC. The only code that I did get was for the IAC.

Do you remember the exact code number?

Codes rarely mean to replace a part, they usually mean a preset limit(under or over) has been reached, so computer is giving driver a heads up.
But that being said the IAC Valve is a mechanical device so will wear out over time.

I don't remember the code but my other IAC wasn't working cause the pin in side was broke and the spring was gone, and it was new, plus I saw a difference when I changed it. With the old one it would idle around 500 and the new one its idling around 1000. Tried unplugging the IAC after it warmed up and it just died. Tried two different ways to check for vacuum leaks, the smoke way and the carb cleaner and nothing. Don't think its a vacuum leak. It was a p0505 code that came up.

I had a 1999 Escort idle issue, high idle, no codes. Turn off engine, restart and everything is ok for a few days. This repeated, then it idled so low that it would not even go up a hill with pedal floored. Finally, a code: TPS (throttle position sensor), replaced it and fixed the problem.

I just replaced the TPS but that don't mean anything.

While the engine was doing its fast idle thing, I tapped on the IAC and TPS but no change. Try that just to see. Check for corrosion on the connectors for both that may be causing resistance on the reading.

IAC valve and the TPS are "learned" devices.
Any cleaning or replacement of these requires you to reboot the computer so it will "relearn" how the cleaned or replaced devices operate.
Unhooking the Negative battery cable for 5 minutes will cause a Reboot when computer starts again.
Or, of course, telling the computer to reboot using an OBD II scanner/reader.

P0505 means the IAC Valve is not responding correctly to computer control.
This can mean IAC Valve is faulty.
It can mean the wiring to the IAC Valve is faulty.
It can mean the computer circuit to control the IAC is faulty.

After new IAC Valve is installed, and computer reboot, the computer will relearn the valves settings to maintain specific RPMs.
RPM reading comes from CKP(crank position) sensor, and engine won't even start if there is a fault with the CKP sensor, so we assume that is working.

Computer has "soft" cold engine idle target RPM, "soft" because it is based on engine temp, so varies.
Engine temp is read by the computer using the 2 wire ECT sensor, this is a sensor not a sender, and is only used by the computer.
There is a 1 wire sender used by the dashboard temp gauge, usually located near the 2 wire ECT sensor.
Engine temps under 160degF cause the computer to increase the idle RPMs, the colder the temp the higher the RPMs.
40-50degf usually will set 1,100-1,200rpm idle, colder will be higher
A faulty ECT sensor could cause a higher idle, BUT(big but).......the computer has a timer that starts when engine does, after about 10-15minutes of engine running if the engine temp is not above 180degF, the computer will turn on the CEL and set a code for the engine temp, "failed to switch to Closed Loop" or similar.
This could happen from a faulty ECT sensor or if thermostat was stuck open and engine could not get warm enough on a cold day, the second one could be IDed by the dashboard gauge also showing colder than normal temp, i.e. under 1/3, normal on most Ford gauges is just under 1/2 after warm up.

As engine warms up "soft" idle will slowly go down, computer slowly closes IAC valve.

Computer will have a "hard" idle target of 700 for manual trans and 800 for automatic.
It can vary as much as 25rpm but usually no more than that, it can also vary by engine, it is based on emissions standards for the engine.

When you turn the key on, the computer will open the IAC Valve all the way, it will then read the ECT sensor temp data.
When you start the engine the RPMs should go up to above 1,500 because IAC valve is open all the way, RPMs will then drop as computer closes the IAC valve to match target idle as determined by engine temp.
If this doesn't happen then there is a problem with the system.

Got a question? The PCM I put in it was out of a 99 5.0 mountaineer with a three pin cam sensor and I have a two pin cam sensor. I don't know if that makes a difference with the PCM or not. The PCM I had in it was out of a 99 5.0 explorer with a two pin cam sensor so? Another thing some said is I could have a bent valve?

Yes, cam sensor matters
3 wire is a Hall Effect sensor
2 wire is a Variable Reluctance sensor

They are not interchangeable, computer is setup to read one type only, there is no "wiring converter" you can use.

You need to install the 3 wire CPS and wiring for it, or get a PCM that can use the 2 wire VR sensor

Bent valve would have a steady single cylinder misfire and you would get Code P030X, X being the cylinder number that is misfiring, i.e. P0305, cylinder #5 misfire

Ok that's what I was afraid of. It just dawned on me that I had swapped the CMP and started thinking about it. Damn that sucks.