Hello,
I'm having an intermittent misfire at idle with no CEL. I have tried a list of thing to diagnose and fix this issue, but I'm getting a bit frustrated. My best guess at this point is a valve or lifter issue. I haven't taken off the valve cover and before I do, I just wanted to see what everyone else thought.
Motor has 103K on it.

Here is the list of things I have done.
Replaced fuel filter and fuel pump, check valve went bad. I know I have good fuel pressure.
Replaced coil pack, wires, plugs. I also tested all wires and plugs resistance, gapped them to spec. Purchased a few new plugs and moved them around with no change.
Power balance test by taking off wires from coils. All had expected power loss change.
I have replaced the crank position sensor
I cleaned the IACV, was pretty clean
I cleaned the throttle body, was also pretty clean
I replaced the DPFE sensor
I check for vacuum leak in the following ways... spray flammable, smoke test, vacuum gauge (needle drops slightly with misfire) everything else was good.
I have cleaned the mass air flow sensor
I sent in the injectors to RC's to have them cleaned. (3 were dripping and low, but this didn't fix my issue)
Replaced intake manifolds and throttle body gaskets.
I replaced timing tensioners just for maintenance.
2 of my 02 sensors are new and scanner show them working well for voltage
Fuel trims both long term and short term are normal
Compression test was normal across all cylinders
With accelerator pressed fully, flood mode sounds balanced across all cylinders, no skipping.
I used sea foam in the vacuum line to clean intake
When you put a piece of paper at the exhaust, it will suck it in when the misfire occurs.
0 codes

The only things I have left that I haven't done is a leakdown test, or have a professional use a scan tool to look for power balance test.

Any ideas?

 

See if your PCV valve and plastic piping from it are working. (pure guess)
edit: Where is the crank positioning sensor on that engine?

 

Good call, I forgot to add that I replaced it about 6K ago. It was one of my first things I did along with checking usual rotted lines. Thank you for your reply!