Most likely you had the battery disconnected to remove the transmission. As a result, the Engine Computer lost its memory. All the fuel trim data and sensor values will be relearned without you even noticing, except for "minimum throttle". That requires a specific set of conditions to be met for that relearn to take place. Until then, idle speed will be too low, the engine may not start unless you hold the accelerator pedal down 1/4", and it will tend to stall at stop signs.
To meet the conditions needed for the relearn to take place, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals.
Friday, October 9th, 2020 AT 7:57 PM