My 1990 F250 4x4 with a 460 ran great then all of a sudden has a rough idle, and as you go to step on the throttle will stall. I've pulled the codes, and get:

KOEO: 11
CM: 11

If I'm reading these right, that means according to the "system" it's fine

It starts right up, but is almost impossible to drive, unless your on some back road where you never have to stop.

 

Does the truck have two tanks?

If so, does the problem happen on both?

 

Yes it has dual tanks and yes it happens on both tanks, it just started recently.

 

Check the fuel pressure. Each tank has it's own in-tank high pressure pump. There is a common fuel filter and fuel pressure regulator so whatever the cause is will be common to both tanks. Very rare to have two bad pumps.

Could be as simple as a plugged fuel filter.

 

My 1990 E350 has the low pressure pump in the tank which pumps to the frame bowl (two tank selector on two tank trucks) and then a frame rail mounted external high pressure pump after the bowl.

 

The F-series gas engine trucks stopped using the three pump setup after 1989. 1990 and later trucks use the two pump system. Each tank has it's own high pressure pump.