Is your engine the B20F with the D-Jetronic fuel injection?If so,there is a plug that goes into a recess in the water neck for your thermostat that may be reversed. 1 wire goes to the enrichment cct. in your f.i. ecu and the other goes to your ballast resistor of your ignition cct..If reversed, your motor will run pig rich just before it dies.It will also cause your coil to over-heat because the voltage to your coil does not reduce when your motor warms-up.With the motor warm measure across your supply side of the coil and you should only read volts.The solution is easy,just reverse the plug.I know I was there with my 1800 ES.