New to the forum. I know, I need to update my profile. LOL
So here is what is going on. The truck is intermittantly running rough from idle to cruise speeds, especially under accelaration. It doesn't do it all the time, but is getting more common. It does not stall or die at idle, and starts just fine. I have changed the IAC, Cap, Rotor, Plugs(which looked fine), Fuel filter, The injectors were replaced last year. It has 160,000 miles and is still rocking the factory exhaust. CAT clogged, TPS, Distributor worn,...? I'm at a loss. It's is not throwing any codes either. Any direction would be appriceated.

 

I had this issue from day one on my 94 3.9. So far I have done; Plugs, wires, cap, rotor, coil, Switch plate, TPS, Oil sensor, PCV, and O2 sensor and I adjusted the TV cable. All of that improved how it ran but still had acceleration lag time and lack of response. Then I did the Timing chain adding a tensioner (you may need a tensioner I forget what year they finally started putting them on at factory) and I did the Hughes engine Intake Plenum kit, IAC and MAP. The intake has a design problem that causes a lot of what you describe. this applies to all size Dakota motors. The plenum is sheet steel bolted to an aluminum intake. The dissimilar expansion contraction destroys the gasket then oil/coolant leak in.
Once I did that the improvement was even more but there is still lag time and not quite the umph that the motor should be giving. I have discovered there are some Dealer PCM updates and I am hoping that fixes the issue. My RPM's don't get over 2k very often and even then only for a moment or two. I think that might be what the PCM updates are for.
If that doesn't fix it I may get a performance PCM.

 

How did you check to see if your Plenum gasket was leaking? I haven't noticed any coolant or oil consumption loss. Not sure that is the culprit. I'm going to check the slop in the distributor rotor. I think it should be around 5mm of movement. If it is more I'll adjust the timing. I have heard that the bushing can wear and cause issues like these. We will see.

 

The problem is identified by the symptoms;
1. Excessive oil consumption
2. Heavy spark knock under load (sounds like a can of marbles when you have your foot in it)
3. Truck feels like it was castrated (loss of power)
4. Trouble getting up hills
You can also look into the intake with a light via the Throttle Body to see if there is any oil in the corners. I wasn't consuming any liquids I noticed either but the bottom of my butterfly valve on the TB was oily. That was good enough for me. There should be no oil in the Intake or TB.
The Timing is set by the PCM, you cannot adjust it. You can rotate the motor to TDC and then get on top of the motor and looking down over the rotor there is a mark on the Switch Plate (cap off) that tells you if the rotor is centered on number one cylinder. Apparently you can loosen the bolt you might think is for timing and rotate the distributor to get that aligned. According to what I have read that is adjusting the cam not the timing. The guy who wrote that up says he went back and checked some of the vehicles he did this way when he got a machine and he was always within 2 degrees of dead on which is within the specs for using a machine. When I did the timing chain I still had the intake off and I looked mine was aligned so I didn't do a thing to it.
Whatever you do it will take the computer probably a full tank or more of driving to get adjusted to the change.
I have recently discovered there are Flash updates for my PCM and I am going in to have it checked/done at the dealers. That is something else to consider. The place I'm going to told me $49-$98 bucks for the job and they will look for codes too. (edit-oops repeating myself)

Have you done the off/on thing with the key to get your codes?
It's 3 times fully on without starting to off then on the fourth time you stop and watch the check engine light. It will flask with short spaces between them until it gets to the first number then pause a bit longer and flashes with shirt spaces for the second number of each code. 12 means the battery has been disconnected in the last 50 starts 55 means the process is dine.
Look in the FAQ page for the code list. Its a lot of stuff to read but it is worth the effort there is a lot of work from people who came before you meant to help you avoid their mistakes.
Good luck Keep us updated.

 

I'll check the codes again. None the last time I checked. I'll also double check my intake. I have a boroscope and can get down in there to see really well. I didn't notice my TB was oily or anything when I gave it a tune up this past weekend. I am going to swap out the exhaust and remove the cat and see if that does help at all. It needs to be done anyway. Hopefully I can get that done this weekend. I will update with what I find.