Rebuilt ECU, now low idle

[fixkick]

The mt ecu did run ok. I jumped the wires yesterday with a/t ecu and code 12 popped up.

does the DP work,  dash pot,  (aka. cold start fast idle device,  it must be extended (has a hidden internal springt_) that holds the trottle valve (TV ) open
even parked key on pock and even cranking and even for 15 seconds first started up.
the ECU runs that thing, via a VSV valve.
this is first.  this device, if dead the engine wants to flood, and foul spark plugs started.

the using foot, you said, well how much foot is that 1/2 or full throttle. as the later mode , causes CUT FULL mode, aka,  clear flooding mode.
or just after it starts only is the problem and  needs right foot,. action.  but if yes, that, then how long, is that, 1 seconds or  minutes/?  need to know all those details to know whats up.
sure seems like bad ECU,  the MT runs the engine the same way as the A/T.
but that assumes the wiring from the shift lever on the 3sp makes it to the ECU, as there AT start wire there, no MT harness has that.
the A/T psu, knows the car is in park and when set to drive, on the stick lever, goes to aggressive idle mode that no MT made can do.
but lets start at the DP.

its on the left ide rear here.right now on the bench it is holding the throttle TV open,  in fact if operated on hot engine rpm is 2500 just it, but that is only test.
2500 rpm calib, is the top with painted screw here, not the black plastic CAPPED no touch screw below.
I cant see your car nor see what is missing and for sure if this thing  is dead, or jerry rigged. in some way , seen on many super old cars.
the ECU controls this 100% nothing else. it must work.
one test on this old TB, is injector leak test, see it spray hot running, (top horn pipe off) and then cut the key, off, 2 persons again, and see if the injector cuts all  fuel  key off in INSTANTLY, key off,  it must. or engine will want to flood next start, this is  all normal tests on all FI cars and lots and lots more tests.
good code 12, means no shorted or dead sensors. not that they work right ever just NOT DEAD.
TB rear view.