Mixture Tuning Chevy TBI circa 1990

[James Ray Crenshaw]

I have just signed up, please flame if I'm posting to the wrong one of the
three lists to which I subscribed.

I have a 1990 Isuzu Trooper with the GM 2.8-liter V6 and TBI injection
system. I'm told that if you've seen a Chevy S-10 from this era, then you've
seen the Trooper.

I would like to try leaning the mixture JUST A BIT. Theory tells me ("I
think,
therefore I err") that some kind of resistor in-line from the coolant temp
sensor
(with a two wire plug, in intake manifold, just forward of the throttle
body) to
the ECM just MIGHT accomplish this. Of course, my being a gearhead, the
neatest thing would be doing this with the ability to tune the resistor...
assuming
it would work.

Who's done it?

Is this a good way?
Is this the best way?
... or is it even _A_ way?

There seems to me to be a pretty wide swing in whatever routine the ECM runs
at idle. Idle speed is steady, but only reasonably do. Is it possibly
staggering drunkenly between full-rich & full-lean while idling?

The exhaust smells of unburned hydrocarbons, though not excessively so. I
hasten to add here that I am NOT trying to "make up" for any running
deficiency. At 127,00 miles it runs great, and always has.

I would like to hear real-world experiences with how many miles the
injectors might be good for. Fuel mileage is 19-20 in town, which I am told
is exceptionally good for this vehicle, which is an above-3,000 pound hunk
of steel. I have replaced the TPS (throttle position sensor), the thermostat
(with one which has the rubber ring intact. Voila! temp gauge began to
move...), the exhaust system and the O2 sensor (w/Bosch unit... which is
what they had at the parts store).

It ran well before, and it runs well now.

I would also like to be able to adjust the idle speed. Can I MINUTELY fiddle
with the minimum air adjustment (adjusts throttle plate position) without
screwing something up? I only want to lower it about 100-150 RPMs.

What say ye?
jrc in SC