Idle Speed and Air Temp/Humidity Options

[StarBear]

As getting ready for the 2022 Northeast Gathering, I'm encountering a semi-recurring idle issue on my 1974 1.8L LJet FI. When outside air is cool and dry, idles just fine at 950-1000 rpm. When outside air is warm and humid, after warmup the idle falls off to barely running. I've just been adjusting the air flow screw (maybe 1.5-2 full turns) to open it. Of course, the reverse happens - if I preadjust the screw it idles near 1800 then settles down to 1100 after the engine gets totally warm (15 mins or so).
I presume (?) there SHOULD be some regulation, perhaps with the ECU or AFM, to monitor air temp and humidity and make adjustments automatically? I didn't have to manually do this adjustment in the past.
The AAR works and tests out fine. Just annoying to have to pull over after running a while and adjust the screw. (IMG:style_emoticons/default/dry.gif)
Your thoughts @Van @Van_B and @Wonkipop ?

[wonkipop]

ok @StarBear .

i had to keep digging. as i do.
i think we do have a temp sensor I on the 74.
but its different to the 75.

i've never been inside my AFM.
so i'm going blind here off documentation and diagrams.

but as far as i can guess or surmise, its somehow inbuilt in our 74 AFM and it appears to have been separated out in the 75 units. perhaps in order that it can be replaced.
i think it is integrated into the potentiometer section of the AFM in 74 but it might have been shifted to another location in the 75 unit, more directly in the airstream.
i have never seen a 75 unit, and being down here, i never will.

but here are the electrical diagrams from factory manual.
this would imply its not there in 74.
but not necessarily. it might be that its just considered an integrated part of the AFM potentiometer unit.




this is the 75 wiring diagram.
clearly says its there as a separate thing.
it has a dedicated pin too. 27.





74 AFM. 6 pins. no dedicated pin.



75 AFM. 7 pins. 27 is a dedicated pin according to wiring diagram. hence additional pin.




diagram page from factory workshop manual.
seems to imply the sensor I is there in 74 and is integrated part of potentiometer.
but is not in airstream.
of course it is a diagram. and i have never popped the lid to go in there and see.



so.......maybe that training manual i downloaded from mr. b's site is not incorrect.
here is the page in question.
interestingly it tells you to test it using pins 6 and 9.



so i am thinking it is there.
but if it screws up in the 74 there is not much you can do about it.

(i leave this with @Van B - i think he has opened the lid on his to look inside). (IMG:style_emoticons/default/confused24.gif)

[StarBear]

(i leave this with @Van B - i think he has opened the lid on his to look inside). (IMG:style_emoticons/default/confused24.gif)

I’ve had mine open in the past and don’t recall seeing anything but the pins and tracks.

[Van B]

(i leave this with @Van B - i think he has opened the lid on his to look inside). (IMG:style_emoticons/default/confused24.gif)

I’ve had mine open in the past and don’t recall seeing anything but the pins and tracks.

I've got one AFM that I did a full tuning session on and there's nothing like depicted up top.