Suggestions Needed to Fix Idle Quirk

[Hib Halverson]

I have this frustrating idle problem.

Maybe you guys can help.

The engine is an LS7 with a 102-mm throttle body, MSD intake manifold, stock injectors, ported heads with stock valve sizes, an aftermarket cam (220/[email protected], .615/.648 lift, 116 lobe sep) and stock exhaust manifolds.

With the manual trans in neutral, I've got the engine where it idles reasonably smooth with no surging, however, it has this weird quirk that occurs I either blip the throttle or hold a high idle speed for several seconds then quickly lift off the throttle.

After I blip or lift off the throttle, TPS drops and rpm drops, but the spark appears to stay on the high octane table for too long rather than immediately going to the idle spark table. Also, after dropping to idle level, the TPS increases again. Since the higher TPS causes RPM to momentarily "hang" a little high, adaptive spark pulls timing trying to bring the PRM down to the 700-RPM desired idle. This "quirk" continues for a while until TPS finally comes back to idle, adaptive spark "relaxes", timing goes back to the idle spark calibration and RPM gets back to 700.

Anybody have a suggestion on how to fix this problem


BB2.81.hpt
Layout021319.Layout.xml
19-02-13 14-45-00.hpl

[Hib Halverson]

I was a little surprised that none of the idle cal experts replied but after some further Internet research and some trial-and-error, I've done some changes that have greatly mitigated the problem.