Just picked up an '03 Durango 4.7l a few weeks ago for my girlfriend and have been slowly fixing/working on small things.
Two days ago I was following her and noticed that it puffed out some smoke a couple times!!!!
I've been doing a lot of research and am trying to track down what is causing it. Here's what I know..

-It's not a head gasket. Thank God.
-Doesn't smoke on startup
-doesn't smoke when cruising or idling

It only puffs smoke SOMETIMES when accelerating. Or if you sit for a minute then rev the engine. Only SOMETIMES. it doesn't puff every time you take off or rev it.

I wish I could say how much oil it uses but we haven't had it long enough to say. I just changed it yesterday with 5w30 so I'll watch it now.

The possible culprits that have caught my attention so far are the PCV system, plenum gasket, and valve seals.

We're in the middle of moving and I haven't had much time to start physically digging into it much. Just research.

It's hard to find solid articles/posts for this particular smoke issue and particular engine so I'm hoping to start one here!

Anybody have any knowledge or thoughts on what is causing this? Or even what's not causing it?

 

Worn valve guide seals. I'd not worry until it gets worse. You do want to keep an eye on the oil level though. Sometimes the converter will clear the smoke when you burn oil.

 

According to my research it consistently says that the smoke is the worst during startup when the valve seals are bad. But I don't see any smoke on startup warm or cold.
Is this not always the case?

 

On cold starts, everything has contracted. When it's warmed up, the clearances expand, the oil thins and so on. I had a Lincoln TownCar that wouldn't smoke on start up but would when warmed . Sometimes when I was sitting at a long light, I'd leave a HUGE cloud of blue smoke when I'd take off. I got cussed more than once with that car.

 

Did you ever do anything to either fix it or combat it?

 

Replace the valve seals. Not sure just how much of an ordeal that would be on an OHC engine......

 

I swap cars a lot. I planned to but got offered enough money it got for sale quick. We don't have emissions testing so I wasn't in any hurry.

 

May also be leaky injector/s dumping extra fuel into cylinder/s.

 

A little extra fuel will smoke black. A lot of extra fuel will smoke white and may smell like gasoline.