Well still have the problem, only now it seems isolated to speed in the 20-30 MPH range (2 gear). Replaced engine coolant temp. sensor and found some cracked vacuum lines and replaced them also. I think it is either a fuel issue or electrical (firing problem?). Very frustrating. May try the ignition coil next.
If my check engine light is not on can codes still be pulled?

 

Yes, pulling codes should be the first step when trying to diagnose any problem. The engineers only selected a handful of codes to trip the CEL, the ones they deemed critical to the engines health, the other 300+ codes won't trigger the light but could still be thrown.

 

Mine was a fuel pump going out. Would start and run good at idle, and when slowly pressing the gas pedal. When trying to pass or getting on it. It would stumble and run rough. Changed the fuel pump assembly and runs great now.

 

Well finally gave up trying to figure out the problem and took it to my local mechanic. Sure enough fuel pump is bad.