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Hi,
I have torn these things open.
I have found out that the brushes wear grooves into the commutators.
This is like an electric motor but it makes partial rotations only one half of the commutator.
The grooves that this creates very slowly, eventually get worn deeper in the areas it works back and forth the most.
One end of being deeper has tapered in width the groove also gains height changes.
This moves the brush up and down in their holders some while all the time getting shorter just like in our alternators. This lessens spring pressure.
This movement, up and down can allow the brush to float and even twist ever so slightly in the clearances of the holder that can get dirty from dust.
When this happens the brush can break contact with the groove.
A little arcing can smut up the surface of the groove during all of this wear accumulation.
So this can cause the IAC to hang up become sticky.
Add in some low voltage moments during starting the car can cause delays of action.
In others words, it has become lazy, tired or just plain worn but not bad enough to totally quit causing erratic idle behavior.
Much like in-tank and main fuel pumps causing hard start issues.
Ohmmeters have their limitations. I used a lower voltage test procedure to mimics worse case performance of vane swing with a nine volt battery, thats even slightly used, as it puts a limit on current input.
Not a 12 volt car battery.
Yours a little fussy for some years, wow, you are a patient fellow, aren’t you! (:-)
I’m Glad you got the“ fussy one” chased out of the car!
I don’t have kids but I can imagine someone or something being fussy, can only last so long!
Phil
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