mountainmanjoe,,

Of the basics you list the IAC seems to be the most likely culprit.

My other vehicle is an '88 244 DL Volvo and there is little to no comparison in access between the engine compartments.
This is my first foray into disassembling the innards of this 3500 Express, excepting the recent removal and cleaning of the Air Mass Meter.
To date I have only done the scheduled service items.

Do I really need to remove the generator (!) to access the IAC?
Or is this going to be a case of blind fishing to get at the rear bolt?
Can use of a T-15 be confirmed?

From pictures, except for the hole into the throttle body, I do not see that the IAC itself can be cleaned.
Is there a way to test the IAC while it is installed or after removal to confirm the electronics are in good order?
If I am going to pull this part should I plan on just replacing it? Because searching several locations indicates it does not exist.

I do like knowing where I am going before I start.

 

IAC diagnosis. Again from the same manual
https://charm.li/Chevy%20Truck/2003/...m%20Diagnosis/

 

“Doghouse” is a term often used for the engine cover in the cabin -


Remove passenger seat, drawer/cup console & and both lower dash trim panels to fully remove cover.

As for the IAC, I’d recommend just pulling the throttle body instead of the alternator. Chances are good the whole assembly needs cleaning.

 

Wow, I was hoping for something along the lines a continuity and or resistance test across specific pins.
Or removing and wiring it to a battery to confirm operation of the pintle.
All this electronic noise and not being able to sus it out probably creates as much pollution as it is intended to reduce.

I will have to settle for removal and cleaning the pintle and bore.

 

Yes you have to remove a seat to fully remove the doghouse, however you can push it to one side at a time to get in there without removing the seat.

 

The IAC meters air for idle. Hence the name "Idle Air Control" valve. Nothing to do with pollution.