I have a 3 wire O2 sensor which wire coming out of the ECM do i connect it to so that when the car switches from closed and open loop the heating elemnt shuts off so its not constintly on

 

The 1987 ECM was not designed to control an oxygen sensor heater current, so there is no output intended for that purpose. You can use a different output through a relay so the heater will be turned off in closed loop mode, however:



The black wiring is existing, factory wiring. The red wiring and components are what need to be added.

That should be "1987 ECM", not "1978 ECM"

You can use a relay just like the MAF Power relay for the heater control. The relay operating coil will be powered by the same output as the EVAP purge solenoid, since it is only operational in closed loop mode. All the wiring can be done in the engine compartment, since the necessary circuits/wires are already there.

 

sory i dont really no how to read wiring diagrams can u explain it a little to me if you could?