A few weeks ago my truck quit and I had to limp home. It was so bad it wouldn't even start. It ended up being the cat, so I pulled it, broke it all up and emptied it. Now it's all back together, starts and idles smoothly and revs up fine. Driving though is a different story. When driving at low rpms it skips and hiccups. It runs great at full throttle though. Any ideas?

 

O2 sensors might need to be cleaned (or replaced). At WOT (IIRC), the computer goes back to open loop (ignoring sensor inputs).

 

I'm guessing O2 sensors too.

 

i would think 02 sensors also. just had same problem with plugged up cat. mechanic said didnt even see how it was running at all. gutted cat, and now runs great! at idle, it is as smooth as new, and highway speeds, has plenty of power. almost good as new!