Idle timing erratic (1999 JTEC)

[Dwg86]

I've been messing with this for a while. It was dyno tuned by a shop in Kennesaw Ga. The tune wasn't quite correct, so instead of keep paying them hourly to keep messing with it, I bought a MPVI2 to try my hand at tuning it. The JTEC platform is really basic as compared to other platforms. I've had some help from a few guys here on the forum (Thanks [email protected] and hexdummy for sharing some knowledge). Engine is a 5.9, 9.6:1, edelbrock heads, 218/226 @.050 525/525 lift, 112 installed @ 108. Stock intake, stock injectors, dual 2.5 exhaust, nothing crazy.
Fuel trims look dialed in. I'm not real sure about the main timing table the tuner set up. It looks really conservative. I may mess with that some later on. One of the things I've noticed is my idle timing on the VCM scanner is all over the place. Since the computer controls timing, what could be causing this? The IAC fluctuates also. Vacuum at idle is 14hg and is steady. Compression test on all cylinders is 175psi. this is a new engine i built. Cam was installed with a degree wheel so i know its installed correctly.
idle_ac_run.hpl

[Dwg86]

heres the tune
jeeptrucktune080523_56040137aa.hpt

[joefus25]

Did you ever figure anything out on this? Mine does weird stuff too and I don't understand why.

[EvilR/T]

Did you perform an idle sync?

[edcmat-l1]

Both behaviors are perfectly normal. It uses both the IAC and timing to control idle speed. Neither are supposed to be steady @ idle.

Idle synch has nothing to do with it.

[EvilR/T]

I got a hotter 5.9 that his and mine idles fine with a slight lope, it doesn't hunt for a steady idle. If it's hunting for an idle something with that small cam, something isn't set up right.

[edcmat-l1]

I got a hotter 5.9 that his and mine idles fine with a slight lope, it doesn't hunt for a steady idle. If it's hunting foe an idle something with that small cam, something isn't set up right.

It's not hunting for an idle. The behavior of both the IAC and the timing are completely normal.

This is the table for your idle spark. "Proportional gain for idle spark based on RPM error". All EFI systems use spark to control idle speed. The IAC is supposed to move constantly also.

Idle spark gain.jpg

[EvilR/T]

It's not hunting for an idle. The behavior of both the IAC and the timing are completely normal.

This is the table for your idle spark. "Proportional gain for idle spark based on RPM error". All EFI systems use spark to control idle speed. The IAC is supposed to move constantly also.

Idle spark gain.jpg

Totally misread that, sorry. Yes, all that in mine is moving around too, PCM is consistently adjusting.