[1998 Toyota AE101 ] Idles low and shuts off randomly once every few days (Park, Neutral, Drive doesn't matter!)

Hi all, exactly as titled I have this problem with my Toyota AE101 Sprinter Marino Automatic (basically a Corolla with a sporty body).

I'll be honest right off the bat, I am really overdue for maintenance because where I live there has been prolonged state of emergency due to Covid and I'm an essential worker so things were all over the place for me.

Recently this happened around the same time I got engine code 14 (ignition signal I believe) and it went away. 

So far I had the distributor re-sealed in and out, engine bay fuel filter changed, injectors and throttle body serviced, and spark plugs changed.

The code never came back but I still have to service the transmission as well. I also noticed while in Drive gear, the car is in a sort of limp mode where it shifts early and can't get passed like 2K RPM but there was no Engine light or Code for this yet. 

My mechanic told me to change the knock sensor when I come to service the transmission to solve the problem, but I've already changed this sensor 2 years ago and I know these can last like 10+ years. 

Do you all have any suggestions? Much appreciated.

-Brian

(old car struggles)