[Diy_efi] desperate need of help

Michael Opp oppie501 at yahoo.com
Wed May 28 03:29:32 GMT 2003


I have a 1991 k2500 with a 350 t.b.i. motor.  I have
recently rebuilt the engine and decided to upgrade.  I
installed edelbrock aluminum centerbolt heads with an
aluminum performer intake, with an adapter plate to
use my t.b.i.  I installed a comp cams oe roller with
206 degrees int. and 212 degrees of ex. duration at
.050 lift.  The lobe lift is .320in and .325 ex. the
cam is ground on 112 lobe seperation.  I had a custom
prom made by an aftermarket company.  I have spoken to
them many times and cannot get any answers for my
problem.  The engine idles pretty good in open loop. 
Once in closed loop the idle will not stabilize.  It
will surge up and down about 200 rpm.  I have checked
for a vacuum leak and have none.  The block learns are
around 114 at idle and map kpa is about 44.  The iac
counts stay steady around 20 to 24 counts.  Under no
load in park while holding the accelerator steady
about 1500rpm the rpm will flucuate up and down about
100 rpm.  The engine runs well under load.  I have
checked the usual things like compression, valve adj.
vacuum is good at around 21 in hg.  I spent time
drifting propane around all vacuum fittings and into
the crankcase to check for a leak under the intake. I
can't find one.  I need help to determine what the
problem is and how I can go about fixing it.  I wound
appreciate any input.

Thanks,
Mike Opp


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