Unexpected AIS behaviour

I don't have problem per say just looking for possible root cause.
I have an 87 Ti log and the AIS needs to be cleaned of carbon every 7K miles or so. Which is a 10 minute job. When I purchased the car new, the idle was set to 950 rpm and everything was fine. I decided to readjust the idle to the factory 800rpm as per the FSM, I noticed that the bypass airscrew was set to 950rpm rather than the standard 600rpm, this of course was with the AIS closed. 98.6% of the time the AIS works as expected when clean. Now here is the strange part, if I drive at 50 mph for 10 minutes straight and then need to stop at a light. The revs commonly drops to 6-700 which lead me to believe that once I am cruising for the bit the AIS closes. This is most noticeable with a high electrical load due to winter conditions...lights, heater fan as you would expect. I realize this is easy to fix just bump up the air bypass adjustment and I am done.
My reason for this message to understand why the ECU would close down the AIS entirely.

my guesses.
Perhaps only a log AIS thing as the ECU does not know the position of the valve thus it close. The ECU should know the 88+ AIS position since it is a stepper motor

a guess for closing the AIS completely might be the long intake tract AFTER the throttle body

I've read years in the past ,adding the top mount intercooler and extending the intake tract as a result causes a stumble or issue for the AIS also on deceleration

In a way that is sort of strange, most ISC systems are supposedly programmed to go full open on deceleration until close the desired idle speed. This is to prevent pulling oil past the rings and valve guides from high vacuum conditions. I don't know where in the software this resides on the Chrysler strategies, on my Ford EEC-V system it is actually called a "dashpot" setting and is obviously different for ATX and MTX applications. As far as "knowing" where the AIS is, the later stepper motor does a quick close then open at key on to "locate" the closed position.

On the Ford systems, the ISC is a duty cycle solenoid so there is no reference position on those, it is rpm/road speed controlled, where over a certain speed it is fully open (loss of power or control results in it closing fully). Is the LM getting a "distance sensor" signal? Loss of that can cause it to not know that you are coming to a stop. I know that on the later systems, the control logic for idle varies between ATX and MTX, an MTX computer (LM, SMEC or SBEC) will drop the rpm back quickly after a throttle "snap", where an ATX will "hang" briefly if in P or N even though at least the SBEC has a P/N input signal.

Quote:

---

Originally Posted by 85lebaront2

Is the LM getting a "distance sensor" signal? l.

---

Yes as the scanner shows speed and the LM shows no error codes.