Rough Idle and Running Issues

[gsdk94me]

To All,
I am new to the site as far as posting but I have spent hours reading. I know these questions have been asked but I still can"t get my problem fixed.
Here is what I have:
91 F150 XLT Lariat This truck was inherited recently by my son from his great grandfather and has 41,000 miles on it. When we got it we drove it around some and never had any issues. We stopped driving it for a couple of months and now it runs terrible. At first it would start and run fine and then after warm up it begin to run rough. Skipping and idling rough. As time has gone on it has gotten worse. This is what I have done:
Fuel pumps
cleaned fuel tanks
fuel filters
new ICM
new ECM
Deleted EGR
Trouble codes are:
126
411
538
536
632
412
I reset timing with the engine warm, in neutral, brake set at 10 degrees without the plug in. The engine would run ok for about 2 miles and then you can literally feel the truck power fall completely off and will barely run 20MPH. I am at my wits end and cant figure out what is going on. PLEASE HELP ME!

 

[O'Rattlecan]

126 - MAP Sensor out of range (vacuum)
411 - Cannot control RPM during KOER low rpm check
538 - Invalid cylinder balance test due to throttle movement during test
536 - Brake on/off circuit not activated during KOER
632 - Overdrive transmission code (likely not related)
412 - Cannot control RPM during KOER high rpm check

The one that sticks out to me the most is the first code, 126. I think you might have a vacuum leak somewhere.

Ryan

 

[flareside_thunder]

I agree with what Ryan said. What engine?