My Idle RPM's surge back and forth from ~800 to 1500 when I first start the engine. Cycle time is ~ 4 or 5 seconds. This is a Cold Engine Open Loop issue only. It's not all that cold here, maybe 40 deg. or so. When the engine warms up a bit or goes into Closed Loop all is good. It did this last winter too, but stopped doing it at some point. Started doing it again again last month. Is there a constant or table that I should try tweeking? I'm using a modified ANZA bin with 6E.

First check that the MAF to pipe connections are sealed. Any tiny leaks will cause lean-ness which in turn causes surging. The MAF may also be dirty. Check that the burnoff works correctly.

Look for cracked vacuum lines that are bleeding air. PCV valve that is hanging up.

In the tune it can be too much or not enough SA. Or the AFR is a little lean in areas. If the injectors are not stock the injector compensation tables may need to be tweaked. Cold starts usually have the vehicle voltage higher then on warm starts.

RBob.