Help- Idle is driving me NUTS!

[Programmer]

Sorry--missed your original post. I don't know if this applies or not, but I
know I've seen TSB's about O2 sensor placement in some 4.3's to improve
overall low speed driveability. Your unit is trying to pull more fuel out
when in closed loop--even though you've lowered the low MAP fuel tables more
? Your O2 crosscounts should be around a  half to 5.0 Hz--so I don't think
that's a problem. Higher CC's are indicative of a miss-fire or problem--are
you sure your exhaust system is 100% tight ahead of the O2 sensor ? IAC
counts are ok--and really don't indicate any leaks if idle is correct. MAP
is good for a mild cam--not much more duration than stock. Sounds like false
O2 past the O2 sensor to me...
Lyndon.
-----Original Message-----
From: Reid Bishop <rbish at ibm.net>
To: gmecm at diy-efi.org <gmecm at diy-efi.org>
Date: October 10, 2000 5:17 PM
Subject: FW: Help- Idle is driving me NUTS!


><I apologise if this is a repeat- I swear the two times I sent this message
>out before, it never made it to the list...>
>
>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.
>
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