142k miles. Started about a month ago No Codes, No stored codes. 1100-1500 rpm's runs like a misfire. Previously getting 425 miles to the tank around town, now getting less than 300.(A little Background) In the past year i've replaced; all my COPS(accells), 23 lb/hr Injectors, Idle air control valve, EGR, fuel pump and assembly, upper and lower intake gaskets, front main seal, head gaskets, cam position sensor, coolant temp sensor, thermostat, all four O2 sensors, lots of crap to get it running as new. Compression by the Ford Computer, is at 100% in all 8 cylinders. I'm at my wit's end i just replaced the fuel pressure regulator as a last ditch effort, hoping it was a fuel problem.

 

Check to see if you have a vaccum leak.

 

I have looked, with my ears eyes and carb cleaner. Not that i can find. Ive been replacing any hoses that are even questionable. I'm lost.

 

you replaced the COPs but not the spark plugs?

 

Sorry Moro raft iridiums last week

 

Bah response was from my phone. Motocraft iridium not moto raft

 

Clogged cat?

 

Ford computer system said all four O2's are working and show proper amount of exhaust fumes

 

More clarified post of the condition, sit in park raise rpms to 1200-1350 once it hits that area it will fall lower then rise to meet previously stated rpms then fall and rise again etc etc. Condition feels like a miss when driving at idle speeds 45+. Also present in acceleration

 

did you try cleaning your maf sensor?