Re: FW: Help- Idle is driving me NUTS!

[ECMnut@aol.com]

I scoffed at the idea at first, but after I put a cam in my 4.3 mpfi turbo,
and the BLMs were below 100, I trimmed the "closed throttle VE" tables
 until blm was close to 128, then becuse the idle still sucked, I maxed 
out the C/L enable temp, so it is always in open loop. 
 I use the o2 sensor to tune, but I shut off the ECM based corrections
 for the sake of a smooth idle with MAP & a slight cam.  I know it's a 
cop-out, but it works.
HTHs
Mike V 
> 
>    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.
>  
----------------------------------------------------------------------------
To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
in the body of a message (not the subject) to majordomo@lists.diy-efi.org