That "ECU ground wire" as you called it is actually the OX sensor
reference ground!

That ground wire is critical for exactly the problem he is having but it
has nothing to do with the temp sensor. It relates only to the OX (O2)
sensor.

Mark

Gregory Smith wrote:
> Mark,
>
> I'd test and/or replace the coolant temp sensor, as this variable
> resistor is the primary source for information on air/fuel mixture for
> the engine.
>
> I had a similar issue recently and after a new sensor was ineffective,
> found the ECU ground wire near the distributor was broken at the ring
> terminal.  Installed a new terminal and my issue was solved.
>
> Gregory Smith
>
> Smith Design Studio
> Small Building Company
> Olympia, WA
> 360-239-0429
> gregoryfsmith.com
>
>
>