LSX454 w GMPP E67 ECM - Idle Surge
Working on a GMPP 454 LSX with matching GMPP E67 ECM and it has a bad idle surge. Surging a few hundred RPM, mostly shortly after start up when it transitions from cranking to running. Looks like timing is the main culprit, but it affects everything else. I've played with min idle air, base idle timing, high octane timing, prop gain for idle, idle under/over timing, closed/open loop, etc. Better, but still there. Do the maf readings look too choppy? I assume cam reversion? There are points when the TPS does not move, but the idle is swinging a 150-200 RPMs, from timing. It's weird, as if I'm fighting another issue, outside of the tune.
Any ideas?
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