IAC modifications

sfg sfgent at ac.net
Sat Nov 29 20:34:06 GMT 1997


bruce plecan wrote:
> 
> After installing too big of cam in a GM TBI system.  I say too
> big, cause numerous chip programmers said it wouldn't work.
> At one point in time I had a huge problem with the idle speed
> being erratic, and hunting around.  With the scanner I could
> see the IAC varing.  So after much experimenting I had some
> new cones machined for the end of the AIC shaft, as I recall
> they are a 6-32 thread.  Had only about .015" taper for the
> lenght of the cone, and then used an electric drill, and
> file to get the taper right for cold starts, and hot idle.
> While the computer uses the IAC during cruise conditions, I
> never experienced any problems, with cruise conditions with
> the custom taper cones (pintles).  Final cold idle was 1,100
> rpm, and hot idle 650-700, and electric rad. fan has only min.
> effect now on idle speed.  Also, bought a stepper motor
> controller kit, at an electronics store, slowed it down, and
> put a GM connector on it, so I could run the pintle in+out
> on the bench, rather then having to go thru the IAC routine.
> Had a spare TB housing so I could set it, on the bench.
Bruce,
What are the specs of the cam you are using, and are you still
using the original chips? This is a very clever idea! Steve



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