97 Dakota (loss of power and backfire)

Hey, we are talking about family here.
HISTORY: 97 Dakota, Ext Cab, 135K, 3.9L, 2WD Automatic.(oil changed every 3K, without exception)(Rotela).
About 4 months ago I noticed an occasional backfire(no code set).
This progressively became worse, with a noticeable loss of power. About 2 months ago, it set a misfire code(misfire on #2 cylinder). I changed spark plugs, rotor, distributor cap, and spark plug wires.(no favorable results). About a month ago it set a misfire code on 2 & 4. It only sets codes occasionally not every time out. I have a OBD2 code reader, and the freze frame gives me no clue as to what is wrong.
CONDITION OF THE TRUCK NOW: Starts good, has a slight lope at idle(barely noticeable ). Put your foot on the brake and shift into Drive or Reverse and the lope is very bad. Driving,it is very weak on power, and when you floor it(unless passing gear kicks in) it is so weak it is hard to get into interstate traffic. And with the throttle full open it backfires almost every time.
WHAT I HAVE DONE(not mentioned above) I have, to my satisfaction, eliminated the following(right or wrong). No vacuum leak. Fuel preasure is OK, Compression test is OK. Run fuel injector in gasoline twice. Back preasure is OK(disconnected exhaust ahead of cat-conv). With a digital volt meter I have found the following items to be with in tolerance. Battery Temp, Air Temp, Coolant Temp, Map sensor, IAC valve motor, Cam sensor. The PCV is like new.
DESPERATE MOVE: I took it to the Dodge Dealership. After 6 hours in the waiting room, this is what they told me. We have went as far as we can right now, we believe the problemto be mechanical, and we do not have a Valve cover gasket. If you like we will make you another appointment and order the gasket. I ask about the appointment and they said it would be 2 1/2 weeks before they could get too it. Theycharged me a diagnostic fee, and said they would probably have to replace the rocker arms(they thought they could hear something loose on one side).
On my way home I stopped by Autozone and bought the valve cover gaskets. Removed the Valve Covers and found nothing wrong. I also found they had re-gapped my spark plugs to .30 not .40 as shown on the sticker under the hood.
MAYBE A CLUE: At an idle, I can unplug the #4 fuel injector, and there is very little or no change in the engine rpm or sound. It sounds as though the IAC valve does not re-lean the mix.
Any thoughts on this matter will be deeply appreciated. I know the truck is old and worn out, but so am I.(It's a beauty, when I had the oil changed the attendant wanted to know if it was an 05).
Best wishes to all: Rogerx
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Some of this might help: check the timing chain for slack, investigate fuel pump
if the chain has slack the computer will compensate to a point. at 185000 my 95 Dakota v6 had enough slack that I literally lifted the chain off without unbolting the cam gear. HINT: if it is the chain get the 318 (v8) it comes from the factory with a tensioner (yes it will fit)
Fuel pump: at about 220000 miles mine started the backfire at wot, I pulled the pump to find that the assembly had "fallen apart" it still functioned but was "floating" on top of fuel, instead of sitting on bottom of tank.
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Billy
1995 Ram 2500 4x4 Cummins
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Rogerx wrote:

My dads 98' dakota 3.9L started misfireing at around 138K. first it was ot to bad but after a week whenever you would come to a stop it would misfire and almost quit running. And also low RPM at idle. Then the check engine light came on and said #5 cylinder misfire and also cloged Cat converter. First he replaced Distb. cap , spark plugs, plug wires, and the coil. After that it ran fine for a while and engine light stayed off for about a week, then it came on with the same two things. Checked the cat and it was clean, replaced both O2 sensors, still no help. Cleaned the IAC it was gumed up and sticking, this helped with the RPM's. Went and got a new IAC and every thing was fine. I would try cleaning the IAC with carb cleaner, because after a while they got gumed up with black stuff and stick not letting enough air, or two much in the engine. You may want to replace the Distb. Cap, plug wires, plugs, and Coil. Got all of this at O' Reillys for About $45. As for the power loss you may want to check your cat converter, when these cloge they cause alot of power loss and bad gas milleage. Its really hard to tell because of all the different sensors and such.
Brian
92' Power Ram 150 93' Power Ram 350 CTD
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