Finally got the truck running right...was skipping and stalling at startup but would come out of it after about 5 minutes and then run like a top. When you first started it, it would sound ok but once it tried to idle down it would go to crap.
Got a CEL P0138 for the rear O2 sensor but after searching posts and hearing that it just monitored the cat it didn't sound like it was the culprit.
It seemed like a moisture problem so I switched out the distributor cap and rotor, the plug wires and the plugs. Some of you may remember the plugs 'cause one of them snapped off in the head.
Still had the same problem but it was getting worse. Kept stalling out and now was taking about 10 minutes after starting it to idle right.
Finally bit the bullet and bought the 'after the cat' O2 sensor and switched it out. Pulled the battery and cleared the codes. Started the truck and it was a bit better but still not right.
My wife took the truck the next day and said it seemed better to her to but she got a CEL light again. I checked it again and this time I got the P0132. Front O2 sensor this time. Switched that one out and cleared the codes again. Started it and she is running perfect.
Don't know why I never got the front O2 sensor code before but that cured the problem.

 

Once it set the code for the Rear O2 sensor it stops testing the front.
It does this because one faulty engine sensor can cause others to appear faulty too.
So to stop false code from setting it simply stops the OBD tests for other related sensors.

Glad you got it sorted out

 

I didn't know that! I kept ignoring it because I didn't figure the rear sensor was causing the problem. Sure didn't take long after switching it out for the front to register the code.

 

The front and rear o2 sensors are a little different. If you look at their pictures online they are designed differently because they are made to sense disimilarly. Maybe you should get the correct upstream sensor.

 

??? HUH??? I did get the correct sensor...you lost me specialist.
I only had a P0138 code come up...rear o2 sensor. So I changed it with a rear O2 sensor.THEN the P0132 code came on which was the front sensorwhich I changed with a front sensor.