4AGE Tranny Idle-Up

[PhilMR2]

Greetings to all!

Hello, I have a newly acquired '86 MKI with a 4A-GE and a Automatic Transmission.

Kindly correct me if I'm wrong - My understanding is that, when everything works right, the idling speed should be relatively constant (say 800-850 RPM) whether:
1) all accessories are off
2) A/C is on
3) With Electrical Load (i.e. headlights or Defogger)
4) Shifted into gear


Whenever I shift from Neutral (or Park) into Drive (or reverse, or any 1st or 2nd for that matter), the Idle drops from 900RPM (when warm, with A/C off) to around 550~600 or so.

If A/C is on, its around 1,000 to 1,100 when idling and drops to around 650 or so when shifted into gear.

Am I correct in assuming that the ECU should bump up the idle speed back to 800 or so?

Put in another way, should the engine "correct" itself (by idling up) when shifting from Park or Nuetral into any gear?

If yes, what could be the culprit if it doesn't (idle up)?

To get a better understanding, what sends the signal to the ECU that it should adjust the idle speed:
A) the N or P detect switch?
B) the solenoids inside the A/T box?
C)One of the vacuum lines?


While at it, how does one adjust the amount of idle up when the A/C switches on?

I can probably live with this (idling slightly higher than normal to prevent engine stalling), but just like you guys, I'd like the MK1 run as perfectly as it could be (not to mention save a little gas). Any help will be truly appreciated!