Sorry 'bout the lack of information. I let the truck warm up then took it for a spin for a few miles to get heat into everything. In park I slowly increased the throttle until it was at 4000 rpm. I did not unhook the pre-cat O2 sensor. BUT! I did find out something really interesting: only one pipe has a cat! It appears someone removed the cat and o2 sensor from drivers side pipe and replaced those parts with a simple piece of exhaust pipe. I see the plug for the o2 sensor zipp-tied out of the way. One o2 sensor is plugged in. I should try to take a pic of this, but it is colder that a witches tit outside and don't want snow landing on my camera. I'll try to get this into the shop within the next few days. I have new plug wires, plugs, and the speed sensor that fits into the transmission (TPS did nothing for the tranny shift-up-shift-down syndrome). Also bought a new tranny filter while I was at it and synthetic tranny oil.
Checked the air filter and it is clean, but will replace it anyways.

 

There is no such thing as a tune-up anymore. The dealer is taking you for a ride. Take your truck to a muffler shop and have them perform a pressure check on the cat. That was the problem with my truck, which I bought used.

 

how do they do a pressure test on the cat? I think mine is goin bad and i want to know before i replace it.

 

They use a torch to cut a small hole in the exhaust pipe before the cat. Then, they connect a special clap that pressurizes a line running to a meter, which indicates how much backpressure there is from the cat when the engine is running. The then weld the hole shut. I doubt there would be a charge involved as it takes about 10 minutes.

 

thanks, time to start calling some muffler shops

 

"only one pipe has a cat! It appears someone removed the cat and o2 sensor from drivers side pipe and replaced those parts with a simple piece of exhaust pipe. I see the plug for the o2 sensor zipp-tied out of the way. One o2 sensor is plugged in."

Well, that's kind of stupid. So the ECM has absolutely no idea what's going on. I can't believe it didn't show before this!

 

Had the same problem on a 88 318 it was a combination problem of a weak fuel pump and old fuel filter.