Mixture Tuning Chevy TBI circa 1990

[CSH-HQ]

>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.

To a limmited degree yes that will work.  But, the ecm swings rich, and lean 
of 14.7:1 AFR, so that the Average is 14.7:1 so only within a slight sindow 
can you lean it.  
>
>Who's done it?

I've done similiar things with MAT, and CTS onna 1227747/8 ecm
>
>Is this a good way?

Not really

>Is this the best way?

nope

>... or is it even _A_ way?

Yes, but better to change table/switch/settings in ecm to do it when possiblle.
>
>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?

See earlier comment about 14.7:1, average.
>
>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.

More a function of fuel quality, IMHO.

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.

Best to change the callibration.
Grumpy
>
>What say ye?
>jrc in SC
>
>