intermittent rich running

[jimbolin]

93 4.0 no codes.Will run fine for a few days then it will run rich to the point of just barely running.When it does this the fuel pump will go past prime when key is turned on.I have not been able to find any shorts or wiring problems.The only things I have not changed out is pcm and crankshaft position sensor.Is there anything else that would make it run rich intermittently?When it runs it runs great.

 

[jimbolin]

Bump, I broke down and ordered a pcm yesterday and already installed the crankshaft pos. sensor....no change.I after hassling around trying to get it to start and run right I thought I would check and see if any codes have come up.I got a 111 in the KOEO test and when I did a KOER test it also did not show code,it did however show 4 cylinder instead of 6 cylinder when doing the cylinder id.It sounds like a new pcm is the right decision.What else should I be paying attention to?Oh yea when it did this I checked coils/wires and they were good.(used induction style timing light)