hello there , i am new to the site but i am hoping for some help. i purchased a 1990 tracker a few months ago and its had an issue where it will randomly start running like a turd and is over fueling and then will stall out and be hard starting after i have replaced many parts that may cause this , i have replaced  plugs, wires , cap and rotor , put on a new fuel pressure regulator and as of yesterday i put another ECM into the thing and its still having the same issue. i checked the EGR and it all seems to be functioning as it should. i was told to check the wire harness plug behind the drivers tail light and guess what the plug was burnt to a crisp, so i rewired the plug and still having the same issue , i have gone though most of the grounds and am even contemplating adding a few more grounds just to make sure. im not sure what to try next any ideas would be appreciated , thanks.

Well quick update . im thinking i may have found the solution , it seems the temp sensor was telling the ecm it was cold so was causing it to over fuel , unplugged the sensor and drove around for 2 hours and never missed a beat , hopfully a new sensor will fix this , kind of a pain in the ass that i replaced many other more expensive parts to find it was only a $25 sensor ....