I think changing your cap and rotor will likely fix your misfire. Those look pretty nasty.

Aftermarket brass terminal cap/rotor will be fine.

 

So I changed the cap and rotor (blue steak brand), and the misfire continued to stick around. I bought a replacement fuel injector for #6 and swapped it a couple days ago. I even cleaned the injectors on that fuel rail too. Once again it did not fix the misfire. I'm beginning to think Master Tech was correct in his diagnosis - that the cylinder casting had a defect and is cracked around the valve seats. My compression test did indicate lower compression on that cylinder (145 psi as opposed to 165 and 180 psi on all the others), but it went back up to 180 psi after conducting a wet test.

Any other ideas of what the issue could be? Maybe a bad timing chain? Bad 02 Sensor? Restricted Converter? Not getting an error code for any of those but wondering if they're playing a role in this misfire mystery.

 

Timing chain and O2 sensors would affect ALL cylinders, not just one, same for the converter.

Another member had an issue with weak signal from the crank sensor causing misfires..... I didn't think it would actually work that way, as I thought it was basically a binary thing, signal, or no signal.... but, as it turns out, a weak signal can cause the PCM to 'see' it, as a misfire... or something along those lines..... and if the signal is weak enough, that cylinder WILL misfire. Putting in a new Mopar crank position sensor solved a fair few of his mystery issues...... (which rather surprised me.....) He had an oscilloscope to diagnose that one though. Likely not something everyone has access to.... and crank sensors ain't cheap for a 'guess'....

 

Well I sent the truck to my mechanic with 30+ years experience, and he couldn't seem to find the issue either. He also mentioned that an older style oscilloscope would maybe find more answers but he no longer had one. Lucky for me my uncle does and is graciously gifting it, so that's my next step... wonder if it really is the crank sensor. My only other guess is a leak in the intake manifold gasket - I was told I could use a hose and gently trickle a little bit of water over the area of question when the engine is at operating temp, and if the gasket is bad then it will suck the water in. But just as a recap for those reading, this is what I've done in the process of diagnosing the misfire (first 3 were in response to a rough idle):

1. Cleaned the throttle body
2. Cleaned IAC valve
3. Replaced MAP sensor
4. Inspected spark plugs and wires, and swapped cylinders to track misfire (which stayed on #6).
5. Inspected / listened to fuel injectors for the "tap tap", and did an ohm test (which all passed).
6. Compression tested:
   1. All cylinders (aside from #6) at either 165 or 180 psi
   2. Cylinder #6 at 145 psi, but increased to 180 psi after adding teaspoon of oil (so a little extra blow-by around the piston ring).
7. Fuel Pressure Tested @ 48 psi (passed).
8. Replaced [corroded] distributor cap and rotor.
9. Cleaned right bank fuel injectors, and replaced #6 injector.
10. Mechanic replaced the ignition coil (as a guess).

 

Spraying something non-flammable around will also show you where any vacuum leaks are. Idle will change.

 

Out of my own curiosity, is there any data that compares metering rates of the Mopar PCV with the generics? Personally, I run the Mopar, but I’m curious how much the aftermarkets deviate. Thank you and Happy New Year!

 

I suppose you could measure how much vacuum it takes to open it. Flow rates after it opens is another issue. What is it compared to the aftermarket? It would be nice if manufactures would list this information. I did find this, It shows some of the differences between manufactures but don't say who they are. Wagner makes a dual flow PCV valve that they are comparing. $129! But it does allow you adjust it to suit your needs.