What would cause codes 172,173,176,177

[94ranger330]

My ranger is running really rough, It is throwing the codes mentioned wich are both side lean and rich but what could cause it. I have replaced o2 sensors, maf, spark plug wires and plugs, air filter. Please help.

 

[MrShorty]

Do you get equivalent codes (136, 137, 172, 173) from the KOER test or do you get a different combination? Have you checked fuel pressure? Gas in the vacuum line to the fuel pressure regulator (FPR)? Any indications from the old spark plugs if it's running rich, lean, or what? Does the condition of the exhaust indicate rich or lean condition?

 

[94ranger330]

I get no KOER codes except 111 but the check engine light comes on from time to time.

 

[MrShorty]

That suggests that the fault is intermittent. If you clear the CM codes and test drive until the CEL comes on, do you always get the same 4 codes, or different combinations? Any consistency to when the CEL comes on?