I tested as described by spraying everything between the AMM and the manifold with carb cleaner, as well as every vacuum hose I knew of. I cleaned the idle air motor (or whatever it is) and tested for function by rotating it to an "unnatural" position and plugging it in to a non-running, ACC/IGN on vehicle.

I tested the cleaner reaction by disconnecting the fuel pressure regulator's vacuum line and spraying into it. Idle dropped then surged.

I did notice a hose disconnected... the hose was cracked and supposed to be connected to a nipple on the throttle body. I am unfamilliar with what it connects to, and what it's for. The black cylinder it and a much thinner pipe (also to the intake) connect to is located next to the washer resivour, and mentions the fuel tank. I never noticed it because there is not vacuum on the nipple it connects to. I cut the tube, and rerouted it so it would reach.

When I have daylight again, I will flood the nipple with carb cleaner, and try to dislodge anything that may be in it.

So, basic rundown: IAC good, no air leaks, unknown tube unplugged, carb cleaner makes me dizzy.
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89 764 GLE 150k/ 86 745 GLE 240k