I don't think the truck has a bad plenum and I am not sure that would have just given out to start causing the problem. When I removed the old 02 sensor and replaced it, the truck ran really well for the first drive and then started acting up again. I re ran the wires according to the bulletin and the truck seemed to run even worse after that at idle mostly. I'm at a loss. The mechanic told me the only code that came up was related to the temperature of the automatic trans. I'm not much of a do it your self mechanic so any advice on where to take it to be checked out would be helpful. Should I take it to a dodge dealer? they want $100 just to read the codes so that scares the crap out of me.
My personal hunch is that this is a sensor or an electrical issue.
Anything else you guys suggest I look into before dumping a lot more money in to it for nothing? Mech said my fuel pressure is not the best but he does't suspect that to be the cause of the problem. How would I diagnose or clean out the cat if that is blocked?
Cheers

 

I had the EXACT same thing happen with a 3.9 I used to own. Replaced the TPS sensor and never happened again. This is my experience and advice. It cured my problem so it's your choice to try it or not.

 

That's why I asked you to remove the front o2 sensor and leave it out while the truck is running. If the truck runs better, then your cat is clogged. If the cat is clogged then your plenum is gone. A clogged cat can suddenly cause misfiring and a rough idle. You can't clean a catalytic converter once it's clogged, it must be replaced. Avoid the dodge dealer at all costs unless you enjoy being financially violated....

 

So I changed the tps and the truck initially ran like crap. I took it out, put it back in and then restarted it. Now the truck idles as it should and seems to be running strong under acceleration. New issue though or maybe not an issue? I notice when I coast (foot off the peddle at or under 40mph) the truck holds a low gear and does not seem to coast freely like it did in the past. Before it almost seemed the truck would go into neutral when foot off the peddle. Is this normal? its also about 100 degrees out today where I live. I have not yet taken it out on the highway to see how it performs but overall seems to be running as it should and accelerates much better.
Thanks for all the advice. This forum rocks!

 

Did you disconnect the battery while you changed the TPS? If not, just disconnect it, leave it for five minutes, hook it back up, start the truck WITHOUT stepping on the gas. Let the PCM relearn the new values for the TPS.

 

Crap, hope I didn't mess anything up... I will try that for sure. (disconnect the battery) I'm not much of a mechanic and didn't think to do that. Great suggestion.

 

Disconnecting the batt. before doing any thing with any of the electronics is the easiest thing their is to do on these trucks, but for some reason is one of the easiest things to forget. You didn't hurt anything.

 

Yeah, no worries.

We all had to start somewhere. Owning a 2nd gen pretty much assures that if your aren't a good mechanic yet, you will be soon.

 

Crap, just when I thought things were going well... Truck started idling a bit rough again, but truck is driving fine. I read in another post somewhere to check for pressure in the exhaust system by holding a piece of paper up to the tail pipe to see if it gets sucked in. Every 7 seconds or so it does... Strange thing is that it really ran well for the first two local drives after changing the tps and continues to run better but not run as well as it did when I first changed it out. Also disconnected battery and all to reset PCm

 

How is your cat? As it gets hotter, it may be plugging up.....

Does it idle rough right away? Or does it get worse in some time frame?