I have been working on my 97 F250 4.6L with manual transmission. I bought it a while back and it has always had some drive ability issues mostly lack of power. The other day it started stalling at idle. I have fixed that problem but still have rough idle and loss of power.
In fixing the stalling I
1 Cleaned the MAF sensor(scan tool shows good response to change in engine speed) no change
2 Disassembled throttle body housing and cleaned
* EGR valve and EGR port. The EGR valve worked, the port in the throttle body was completely compacted.
* IAC valve (tested bad and replaced.)
3 I replaced all vacuum elbows and believe I have eliminated leak potential. This includes PCV line (PCV valve is on the way just to be sure), breather line, and the Idle air supply line. I have sprayed starting fluid on all connections/lines and did not have any engine change.

When I started up my truck I noticed on my scanner that the throttle position was sometimes getting a strange reading. It would drop to 0% and fluctuate more than it had before I had cleaned the throttle body. I assumed I had damaged the throttle position sensor so I replaced the TPS as well.

I am now getting code p0122 after replacing the TPS and my scanner is still showing the erratic behavior. The throttle position will be around 18-20% at idle and randomly drop to low numbers i.e 0%. I tried spraying contact cleaner on the connections and ensuring I have a good connection at the sensor with no change.
While ordering the PCV I was told the most likely cause was a bad PCM. I have also noticed that my scan tool is reading what seems to be a correct RPM while my tach seems to be giving sometimes incorrect or no reading. The tach as I understand is run directly from the PCM.

Is my PCM bad? How do I test to make sure it is? Would having it Flashed fix the problem? If flashing could fix it is the problem just going to come back? Will a PCM from any 4.6l with MT work from 97-03, how specific is the model of the PCM?

Sorry for the long post. Any help or advice would be appreciated.

 

I have now installed a new motorcraft pcv valve, motorcraft spark plug wires, and bosch spark plugs. This was just done as a tune up. The truck does run better but still has idle issues and lean codes. I also looked at the ECM and it did not have any bad spots that I could see.
The part number is F75F-12A650-NB with hardware type ML2-432 and FBA1 in large Bold type.
Driving now I am getting intermittent results on bank 2 O2 sensors and it has shown a code (did not have one before). I do not think they are the root of the problem, however experience as shown me that even if they are not "bad" replacing them usually improves performance. I went ahead and ordered 4 and will be replacing them next week (30$ apiece on amazon).
I still think there is a problem with the computer, it seems like it is almost freezing periodically with the information it is sending to the tach in particular. Can anyone tell me what used ECMs I could use as a direct exchange. I am reluctant to spend 150 on a referb if I am not positive it will make a difference.