I know, this is an unpopular ECM. But I'd love it if someone could shed some light on how AIR works in this ECM.

In Tunercat, all I get are two constants with factory value in brackets:
Air divert disable coolant temp [62.1°C]
Air divert enable MPH threshold [0 MPH]

I don't see any other constants or tables for AIR stuff. Also please remember the factory setup on the 93 Caprice was unheated O2 on driver's side, Y pipe, single cat. Multiport AIR into passenger side manifold ONLY. NO hose to cat.

My setup now is different. I have LT1 exhaust manifolds and have plumbed the AIR into those. I have converted to a heated O2, still on driver's side. But I have dual LT1 cats and an X-pipe downstream.

I want to get to the bottom of how the ECM handles AIR. Given the way the factory setup was connected, can I assume that this ECM has no code for modifying the O2 switching values during AIR injection?

Also, since I have installed the heated O2, I've significantly lowered my cold closed loop timer and min temp for closed loop. Accordingly, I lowered the "Air divert disable coolant temp" to 32°C but maybe I didn't want to do that.

Any insight? Thanks!

 

My 93 Caprice FSM has some supporting information on this system, which I will document here:

Circuit Description:
An electric air control solenoid valve directs air into the exhaust ports or the atmosphere. Air is directed to the exhaust ports whenever the engine is started and the coolant temperature is above about 20°C (68°F) and below 50°C (131°F) and system in "Open Loop" and engine speed below 1900 RPM. When the vehicle is started and the coolant temperature is below about 20°C (68°F), the air will be diverted to the atmosphere for the entire key cycle.

So I guess it's never supposed to inject air into the manifolds during closed loop. Some of the other logic seems odd to me.

I'm going to make sure the solenoid is working properly. If I had air injection when it was otherwise supposed to divert to atmosphere, that could cause my O2 to read lean, and maybe even that "excessive exhaust dilution" issue I saw on the emissions dyno two years ago.