I posted the other day about stalling/high idle especially when first starting after being cold. I found another 240 and confirmed that my vacuum lines are in the correct placement. Today going and coming to work, the car seemed to hesitate and not have the smooth feel it normally had. When I got home, I looked again for something out of the ordinary.....and I found it. The gray junction box on the firewall that plugs together from the wiring harness had one of the wires popped out from the plug box and must have been making an intermittent contact connection. I opened the box up and plugged and taped each together then taped the whole thing to the end of the harness on the firewall.
So far, no stalling. But.......the idle seems to be a bit high, around 900 rpm with the engine warmed up. This morning after the cold start, it was at 1500 rpm. I tried dialing the knob on the throttle body to decrease the rpm per the Haynes manual to the suggested 700 rpm, but I ended up dialing the knob until it stopped turning with just a slight drop in rpm so I turned it back up a little to where I thought it was.....I forgot to count how many times I turned it. Any thoughts? I'll find out how it drives tomorrow morning with the outside air temp at 35 degrees.
Thanks for looking. I'll roll over 377K tomorrow morning too.
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'86 sedan with 377K miles with original engine and automatic transmission

I did use a new gasket. I'll recheck and make sure I tightened all the manifold nuts. Thanks for the suggestion.
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'86 sedan with 377K miles with original engine and automatic transmission

If you are talking about the connector in the middle of the firewall with the Red/Black/Blue/Yellow Blue wires none of those should affect your idle. Those are the Alt Excite, Oil pressure light, Water Temp, and Starter connections.

Important that they all make contact, but most likely not your problem source.

Double Check all of your plug in connections first, pop them off and reseed the ones at the Throttle Body, AMM (sounds like you have been there) and so on. Clean and polish the spade lug connections to the Coil, just had a badly tarnished connection there cause issues on my 86 245DL with the engine cutting in and out.

Good Luck,

PT

I just got to work and the car idled at 1400 rpm at start up this morning, but otherwise ran fine.....until I stopped at a red light and 10 seconds later without warning it stalled out. It started right back up and didn't have any problem until I got to work. I unplugged the AMM and the rpm dropped a little and it sounded rough....but when I gave it some gas, it stalled out. I plugged the AMM back in, all was well with the rpm's at about 900 rpm according to my dash tach. Hope this info helps someone.

Thanks for looking.
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'86 sedan with 377K miles with original engine and automatic transmission

I just did this not too long ago to fix my heat core hoses...

I would retighten all the bolts for the intake manifold.. make sure you got all of them.. 2 bolts/nuts per intake runner.

Did you use a new gasket? if not good luck getting that sealed.

Did you reconnect all the vac hoses, including the elusive one under the intake manifold.

I would also check your TPS switch and wiring. I had mine fall off and cause problems like you suggest.. I just plugged mine back in, but check the wiring and connectors. Did you knock off some sensor connectors, like the coolant temp sesor, or the knock sensor ( not sure if the 86 has one)

I would also make sure your grounds for the fuel management are good.