1993 Dakota 5.2l automatic V8 4x4 with 213,000 miles here.

Had it running okay for several months after doing some repairs/tune-ups. Replaced the Fuel Pump, Oil Pump, Spark Plug Wires, Plugs, EGR valve, TPS, & IACV a few months ago. Everything was new parts except for the EGR, TPS, and IACV which were pulled from a relatively clean motor at the junkyard.

The truck was running pretty okay for a few months, but I would periodically get a CEL with code 27 and the engine would run a little sputtery and lose power. After turning off the ignition and re-starting the engine the issue would usually go away.

Recently a few weeks ago I had a coil wire touching the manifold and the insulation was cracked/melted, so I replaced the entire set of wires again. Truck ran much better for a week or two.

I started getting a little rough idle again, so I decided to clean the throttle body. I pulled it off and cleaned it thoroughly with TB cleaner from Oreilly's (also replaced the TB gasket.) I even checked all the vacuum lines and replaced any old/dry looking ones with new hose. The truck was running much better now and was much more responsive.

Shortly after I started getting the CEL with code 27 much more often and the truck began stalling quite frequently. I would have to put it in park, hold the gas pedal to the floor and crank for several seconds to get it to start up. Seeing as this is an injector circuit code (code 27), I decided to replace ALL 8 of the injectors with brand new ones. I de-pressurized the fuel system, replaced the injectors, checked all the injector plugs, and fired her up. Once all the air worked out of the lines it started easily and would idle, although now it is idling much lower than before.

When I take it out of park or neutral and put it in D or reverse, the idle drops VERY low almost to the point of stalling. If I drive it like this, it seems to drive fine and run relatively smooth, but I'm feeling a little power loss and a small shake at certain gear/rpm combinations. When I come to a stop light and I am still in gear, but not moving I get a pretty violently shaking idle until I step on the gas again. Almost feels like a dead cylinder.

I used a license plate bulb and pulled each individual fuel injector plug and inserted the bulb to verify that the ECM was properly pulsing the the injectors. They all passed, and you can definitely feel the injectors pulsing just by grabbing them while the engine is running.

Before doing any of this work I always remove the battery cables to allow the ECM to reset. I haven't gotten any CEL's since replacing the injectors and driving normally for several days, but the persistent shaking and low rough persists.

Sorry for the wall of text, but I am nearing my wits end with this truck and I simply cannot afford to take it to a shop or just buy a new vehicle so I really need to get it running a little more decently. Can anybody help?

 

I had problems with my '93 Dakota 3.9 litre auto trans stalling when I came to a halt, engine in gear. Replacing the TPS cured the problem. Perhaps you should try a new Borg Warner TPS. This would remove any question about the used part. You did not mention the MAP sensor. Your symptoms sure don't sound like a MAP sensor that has completely crapped out, but might be due to one that's sending a flakey signal to the PCM. Have you ever recovered any other codes from the computer?
As you are probably aware, the PCM operates the engine from a table kept in memory until it has determined the engine is warmed up. The signal for this switch over comes from the single wire temp sensor (the one on the driver side). Operation from the memory table is known as "open loop". When the PCM determines the engine is warmed up, then it operates based on input from the engine sensors. This mode is "closed loop". If your troubles begin once the engine warms up, you can probably discount the temp sensor being part of the problem. The charge air sensor (intake manifold, passenger side, forward) seldom fails, being a simple transistor that responds to temperature.
My first suspect, based on the symptoms, would be the TPS. But what do I know? Here is a fascinating site that may stimulate you to develop your own theory.

http://oldfuelinjection.com

Let me briefly quote from the site:

"this is why unplugging the battery to fix something can work against you. Unplugging the battery causes the PCM to memorize all the current sensor data as base line and normal. If it memorizes a bad sensor, it will take it longer to call it a liar."

The info is specific to (dare I say it?) Fords, but I have found it extremely helpful with my Dak.

 

Something else occurs to me, you mention the EGR valve you replaced came from a junkyard. Did you hook a hand vacuum to it and check for a leaking diaphragm in the transducer? If the diaphragm is blown, engine vacuum will pull hot exhaust thru the transducer, big time. In short order, the hot exhaust will melt a hole in the barb fitting on the bottom of the plastic diaphragm housing (where you can't see it, of course). An inoperable EGR valve can cause a rough idle on its own. Throw in a vacuum leak with hot, pressurized gas being fed directly into it and no wonder if things are a little choppy.