I've diagnosed two vans with same symptoms, both Syncros on the trail,
after splashing through puddles the OXS CONNECTOR and wire was soaked,
the [small] change in the voltage reading caused by the moisture track
caused the ECU to adjust the fuel mixture rich...loss of power and
stumbling. I'm not a guesser or theorizer, but a experienced mechanic.
The coolant temp sensor cannot be disconnected and the engine run normally.

Yes, shorted plug wires, especially the plug caps, will cause the
symptom too, however weren't these replaced? And it would show up as a
solid miss if so.

Daniel L. Katz wrote:
> richard:
>
> most obvious possibility is problem on high tension side of ignition, such
> as mositure and/or carbon tracks in distributor cap, arcing between spark
> plug wires and ground (might see sparks outright, or glow around wires, at
> night), or, even if not root cause, fouled plugs.
>
> O2 sensor very unlikely here, and it can be temporarily disconnected in
> any case to eliminate possibility. ditto temp sensor. O2 sensor and,
> though to a much lesser extent, temp sensor, are high impedence, low
> current devices, so in this context a little contact resistance is
> irrelevant.
>
> dan
>
>