2006 Durango 4.7L ~175k miles. Had long-standing, near impossible to accurately diagnose issues with severe misses in 5 and 7 but only under very specific circumstances. Long story short, I pulled everything off the top and discovered a melted air intake manifold port over cylinder 7 port. It had folded the plastic down so that there would have been tons of turbulence, possibly causing the issue.

Since I was already back in that area and had everything pulled off, this is what all I did:

Replaced:
Valve cover gaskets (there were a few small leaks)
Oil filler neck tube gasket (came with valve cover gaskets, might as well)
Air intake manifold. (New OEM, no yard had one near me)
EGR Valve
PCV Valve (I have the large metal one with the blue plastic top on the right back side of motor)
O2 Sensors (Bank 2, sensor 1 was throwing a code so I changed both front ones, what a huge PITA btw)
Thermostat
ECM/PCM (There have been indications for years that there were problems with my old one, I was able to get one from CarComputerExchange and with the lifetime warranty, it wasn't a bad idea)

Also completed:
Coolant flush and fill
Fully cleaned the throttle body inside and out
Fully cleaned fuel injectors (sonic cleaning, new o-rings on these before putting back in)
Oil Change
Fully cleaned injector port holes and air intake port holes as well.

It should be mentioned that it would appear I am throwing parts, but really in this instance, it wasn't. What it was in this case is that I was already in there and I had spent a year and a half trying to diagnose the problems in a logical fashion to no avail. If I were to guess, I'd say the melted Air Intake Manifold or the PCV valve were the most likely culprits; however, considering the miles I have and none of those other items had been replaced, it was totally a "might as well" endeavor. I will say that the ECM/PCM was more of a parts throw, but it really has helped, I think.

Test drove around town and all was working very well. In fact, it felt as though it was running better than it had when I bought it used 7 years ago. Drove it to work (highway, 60 mph, 25 miles one way) Monday to test performance there, was fine. It is not my DD, but as it so happens my DD developed a knock Tuesday night, so I drove the Durango to work again yesterday. Again, no issues.

Started it up this morning, and suddenly I am greeted with a CEL. Pull out my scanner and get all the lovely 9 codes that appeared all at one time:



For those reading on mobile who may not be able to see it, they are, in no particular order:

C1041 - Chassis (No idea what this is other than Google indicates something related to ABS/Wheel speed sensor)
P0300 - Powertrain | Random/Multiple Cylinder Misfire detected
P0456 - Powertrain | Evaporative Emission Control System Leak Detected (I had this before I did any of this work and hadn't really tracked it down)
P0507 - Idle Control System RPM Higher Than Expected (More on this below, bc I do have some idle issues)
P3037 - Powertrain (No Clue what this is)
P3341 - Powertrain (Also, no clue)

Greys:
P0300
P0456
P1684 (this one makes sense because of battery disconnection, though not sure why it just came up now - I have checked the codes for greys at least a couple times since I did this work and it wasn't there)

When I started it this morning, it did start "hard". Not as in it was hard to start, it started right up, but almost sounded like I was holding the accelerator pedal to the floor when I started it, then the codes came up. I got out to get my reader and noticed a smell of gas for sure.

As far as idle speed - in gear, it is around 700-800 from what I recall and sounds and feels normal. However, in park it is running at 1000-1100 RPM. Though, a few times, when I first put it in park, it will go down to 850 or so but then creep back up but stops at 1000-1500 (What should it be in park?)

Cleared the codes that all went away and drove into work and it drove fine. I haven't noticed any misfires at all, unless they happened on my start this morning. Any ideas why this would all happen at once? By the way, the rubber boot connecting the PCV valve to the intake manifold was still in good shape. Could this just be some weird part of the new computer learning process?