Help- Idle is driving me NUTS!

[Bruce Plecan]

> I'm about to tear my hair out.  I simply cannot get my 4.3 to idle
properly
> (to my satisfaction) after several tuning attempts.  Tried on both a 7747
> and 8062 ECU.  Here's the skinny:

> BLM's are always running 101-109 at idle, no matter what I do with the VE
> tables.  Fuel pressure is fine- right in spec.  Every time I reduce fuel
in
> the VE tables around my rpm/map idle combo, the engine idles WORSE, and
the
> BLM's don't change.  This last change, my idle is precarious, and it
> generally nearly stalls before the ECU rescues it and brings it back for
> another attempt.  Within 5 seconds, it nearly stalls again... this goes on
> and on.
>
> Other possible hints:  Can't get into closed loop by just idling (even
after
> 10 minutes with coolant at 180) in 40 degree weather, yet once it gets
into
> closed loop it stays there, even after extended idleing
> My O2 Cross-Counts move very slowly at idle when in closed loop- maybe 1-2
> per second at best- yet I see fairly full O2 swings, from 120mv to 850mv.
> When in open loop, the O2 cross-counts advance much quicker.
>
> I have EGR basically disabled at idle (Set EGR% to 0 at low map/rpm
> settings)
>
> Engine idles GREAT in open-loop.  Just gets crappy when the O2 comes
alive.
>
> Can't get my IAC's down either (I have no throttle stop adjustment on my
> TBI).  IAC generally runs between 33 and 48, with a MAP of 30-40.
>
> What gives?  Is this a sign of a need for a heated O2?  Bad O2?  Is there
a
> chance an exhaust leak is screwing up the picture?  Am I nuts?
>
> I do have a mild CAM in this engine, along with a Performer intake.  I'm
> sure it's affecting things to a degree.  All other VE's have been much
> simpler to nail down- and I have the engine running great everywhere but
> this darn idle.

Need to just stop take a break, and double check things from the beginning.
Set your timing,
set min idle,
check for vac leaks,
how is the MAP plumbed
Once you have all the mechanics right then look at editing.
IAC counts are alot higher then what I try for.
Some engines take some large timing changes to get a decent idle.
6's with a cam are lumpy,
All I'll address is the BLs, I tune to what an engine wants,
Bruce
>
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