I have been running into a weird occurrence with my dyna. I have had a issue with my real time afr at idle bouncing around from the desired set afr to as lean as 16 to 1. I attributed it to an intake leak as I would have a hanging rev issue at about 1150 rpms when coming to a stop and the idle would drop low on occasion. Here is the catch. I sprayed the crap out of the manifold and no change in anything related to an intake leak. I also checked it with propane.

So I took the manifold down and didn't see any signs of a leak from the seals but when I had my heads decked and ported it was very tight to get back in place.

I trimmed the manifold for a desired .010 gap on each side and reassembled. With new seals.

Started her up and bam. Same occurrence. Checked for a leak again with spray. Nothing. Now, I thought about the iac valve. So I bought a new one and replaced it. Apparently that's not the problem either.

Any further ideas? Maybe it's tune related?
Pv with target tune is what I am using. My idle kpa jumps from about 35-38 when warm if that matters. I will say my afr's are dead accurate off of idle and at cruise. I would think if it is an intake leak it would present everywhere. Also the jump in real time afr seems like it could be on overlap. My cli's at idle are at about 104 when this happens. And I don't see anything weird going on with my ipw. I also even checked already for a cracked butterfly with negative results

Edit: here is a video of it

https://youtu.be/OyY9XxEQ5j4

 

Does the motor lope at idle?

Add:

The lean issue may not be the result of an actual lean mixture but from incomplete combustion.

 

Here is a video of it doing it

 

Just a thought, but is this really a problem ...rather than just what the PV happens to be showing you on the gauge?

My kpa and a few others that I've read quite happily wobbles around by a few kpa - I think the PV is just telling what it reads whenever the sensor is polled, rather than what was the kpa on the last cycle, at exactly the point it matters to the ECU (ECU samples waaay faster than the PV reports).

Same with the O2 voltage readings. My narrowband according to the PV wobble around 0 to 1 volt, yet the average over 10 samples per second for 30 odd seconds is about .7 volt ...which is what the AFR is requesting

Your idle sounds as good if not better than mine and the rpm is staying pretty constant at +-50 rpm or so, according to the gauge.

The hanging revs is maybe a different story, I've had that a couple of times but from what I remember when it happened the engine was HOT! and it would happen if I pulled in the clutch but was still moving. Pull to a stop and the revs would drop down to normal very quickly

 

It's not a problem... It's simply an characteristic of a sampled o2 systems with a lumpy idle.